A Survey on OFDM-Based Elastic Core Optical Networking
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paper_title: Dynamic optical mesh networks: Drivers, challenges and solutions for the future

paper_content:

We discuss the scalability challenges facing the optical networks. Using the architecture based on spectrum-sliced elastic optical path network (SLICE), we demonstrate how the networking functionality can be effectively shifted to the optical domain.
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paper_title: OFDM for Optical Communications

paper_content:

The first book on optical OFDM by the leading pioneers in the field. The only book to cover error correction codes for optical OFDM. It gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented. It contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers. This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. 'This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view, this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks' - Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology.
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paper_title: 24-Gb/s Transmission over 730 m of Multimode Fiber by Direct Modulation of an 850-nm VCSEL using Discrete Multi-tone Modulation

paper_content:

Using discrete multi-tone modulation with up to 64-QAM mapping, 24-Gb/s transmission is experimentally demonstrated over 730 m of MMF by direct modulation of an 850-nm VCSEL and direct detection with a MMF receiver.
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paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
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paper_title: Technology and architecture to enable the explosive growth of the internet

paper_content:

At current growth rates, Internet traffic will increase by a factor of one thousand in roughly 20 years. It will be challenging for transmission and routing/switching systems to keep pace with this level of growth without requiring prohibitively large increases in network cost and power consumption. We present a high-level vision for addressing these challenges based on both technological and architectural advancements.
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paper_title: Optical packet switching: A reality check

paper_content:

This paper presents an analysis of the energy consumption in a number of optical switch fabric architectures for optical packet-switched applications and compares them to electronic switch fabrics. Optical packet switching does not appear to offer any substantial power consumption advantages over electronic packet switching. Therefore, there is no compelling case for optical packet switching.
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paper_title: Simple all-optical FFT scheme enabling Tbit/s real-time signal processing

paper_content:

A practical scheme to perform the fast Fourier transform in the optical domain is introduced. Optical real-time FFT signal processing is performed at speeds far beyond the limits of electronic digital processing, and with negligible energy consumption. To illustrate the power of the method we demonstrate an optical 400 Gbit/s OFDM receiver. It performs an optical real-time FFT on the consolidated OFDM data stream, thereby demultiplexing the signal into lower bit rate subcarrier tributaries, which can then be processed electronically.
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paper_title: Optical Networking Technologies That Will Create Future Bandwidth-Abundant Networks [Invited]

paper_content:

The transport network paradigm is moving toward next-generation networks that aim at IP convergence, while architectures and technologies are diversifying. Video technologies including ultrahigh-definition TV (more than 33 M pixels) continue to advance, and future communication networks will become video-centric. The inefficiencies of current IP technologies, in particular, the energy consumption and throughput limitations of IP routers, will become pressing problems. Harnessing the full power of light will resolve these problems and spur the creation of future video-centric networks. Extension of optical layer technologies and coordination with new transport protocols will be critical; hierarchical optical path technologies and optical circuit/path switching will play key roles. Recent technical advances in these fields are presented.
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paper_title: Ofdm Systems for Wireless Communications

paper_content:

Orthogonal Frequency Division Multiplexing (OFDM) systems are widely used in the standards for digital audio/video broadcasting, WiFi and WiMax. Being a frequency-domain approach to communications, OFDM has important advantages in dealing with the frequency-selective nature of high data rate wireless communication channels. As the needs for operating with higher data rates become more pressing, OFDM systems have emerged as an effective physical-layer solution. This short monograph is intended as a tutorial which highlights the deleterious aspects of the wireless channel and presents why OFDM is a good choice as a modulation that can transmit at high data rates. The system-level approach we shall pursue will also point out the disadvantages of OFDM systems especially in the context of peak to average ratio, and carrier frequency synchronization. Finally, simulation of OFDM systems will be given due prominence. Simple MATLAB programs are provided for bit error rate simulation using a discrete-time OFDM representation. Software is also provided to simulate the effects of inter-block-interference, inter-carrier-interference and signal clipping on the error rate performance. Different components of the OFDM system are described, and detailed implementation notes are provided for the programs. The program can be downloaded here. Table of Contents: Introduction / Modeling Wireless Channels / Baseband OFDM System / Carrier Frequency Offset / Peak to Average Power Ratio / Simulation of the Performance of OFDM Systems / Conclusions
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paper_title: OFDM for Optical Communications

paper_content:

The first book on optical OFDM by the leading pioneers in the field. The only book to cover error correction codes for optical OFDM. It gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented. It contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers. This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. 'This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view, this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks' - Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology.
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paper_title: Data Transmission by FrequencyDivision Multiplexing Using the Discrete Fourier Transform

paper_content:

The Fourier transform data communication system is a realization of frequency-division multiplexing (FDM) in which discrete Fourier transforms are computed as part of the modulation and demodulation processes. In addition to eliminating the banks of subcarrier oscillators and coherent demodulators usually required in FDM systems, a completely digital implementation can be built around a special-purpose computer performing the fast Fourier transform. In this paper, the system is described and the effects of linear channel distortion are investigated. Signal design criteria and equalization algorithms are derived and explained. A differential phase modulation scheme is presented that obviates any equalization.
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paper_title: OFDM for Optical Communications

paper_content:

The first book on optical OFDM by the leading pioneers in the field. The only book to cover error correction codes for optical OFDM. It gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented. It contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers. This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. 'This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view, this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks' - Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology.
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paper_title: Coherent optical OFDM: theory and design.

paper_content:

Coherent optical OFDM (CO-OFDM) has recently been proposed and the proof-of-concept transmission experiments have shown its extreme robustness against chromatic dispersion and polarization mode dispersion. In this paper, we first review the theoretical fundamentals for CO-OFDM and its channel model in a 2x2 MIMO-OFDM representation. We then present various design choices for CO-OFDM systems and perform the nonlinearity analysis for RF-to-optical up-converter. We also show the receiver-based digital signal processing to mitigate self-phase-modulation (SPM) and Gordon-Mollenauer phase noise, which is equivalent to the midspan phase conjugation.
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paper_title: No-Guard-Interval Coherent Optical OFDM for 100-Gb/s Long-Haul WDM Transmission

paper_content:

This paper describes coherent optical orthogonal frequency division multiplexing (CO-OFDM) techniques for the long-haul transmission of 100-Gb/s-class channels. First, we discuss the configurations of the transmitter and receiver that implement the optical multiplexing/demultiplexing techniques for high-speed CO-OFDM transmission. Next, we review the no-guard-interval (No-GI) CO-OFDM transmission scheme which utilizes optical multiplexing for OFDM signal generation and the intradyne receiver configuration with digital signal processing (DSP). We examine the transmission characteristics of the proposed scheme, and show that No-GI CO-OFDM offers compact signal spectra and superior performance with regard to tolerance against optical amplifier noise and polarization-mode dispersion (PMD). We then introduce long-haul high-capacity transmission experiments employing No-GI CO-OFDM; 13.4 Tb/s (134 times 111 Gb/s) transmission is successfully demonstrated over 3600 km of ITU-T G.652 single-mode fiber without using optical dispersion compensation.
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paper_title: Channel estimation for wireless OFDM systems

paper_content:

A channel estimation technique is developed for an OFDM system with multiple transmit and multiple receive antennas. The approach exploits the channel structure in the time domain and the frequency domain. The method is appropriate for OFDM systems operating in a time varying channel. A multi-input-multi-output OFDM (MOFDM) system model is defined, followed by a proposed excitation strategy for sufficient identification of the channel. The estimation strategy is shown to be optimal within the class of linear MMSE estimators. Experimental results of the algorithm are provided.
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paper_title: Bit and Power Loading for Coherent Optical OFDM

paper_content:

We show the first experiment of bit and power loading for coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) systems. The data rate of CO-OFDM systems can be dynamically adjusted according to the channel condition. The system performance can be further improved through optimal power loading into each modulation band.
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paper_title: OFDM for Optical Communications

paper_content:

The first book on optical OFDM by the leading pioneers in the field. The only book to cover error correction codes for optical OFDM. It gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented. It contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers. This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. 'This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view, this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks' - Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology.
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paper_title: OFDM for Flexible High-Speed Optical Networks

paper_content:

Fast advancing silicon technology underpinned by Moore's law is creating a major transformation in optical fiber communications. The recent upsurge of interests in optical orthogonal frequency-division multiplexing (OFDM) as an efficient modulation and multiplexing scheme is merely a manifestation of this unmistakable trend. Since the formulation of the fundamental concept of OFDM by Chang in 1966 and many landmark works by others thereafter, OFDM has been triumphant in almost all the major RF communication standards. Nevertheless, its application to optical communications is rather nascent and its potential success in the optical domain remains an open question. This tutorial provides a review of optical OFDM slanted towards emerging optical fiber networks. The objective of the tutorial is two-fold: (i) to review OFDM fundamentals from its basic mathematical formation to its salient disadvantages and advantages, and (ii) to reveal the unique characteristics of the fiber optical channel and identify the challenges and opportunities in the application of optical OFDM.
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paper_title: Low-Cost and Robust 1-Gbit/s Plastic Optical Fiber Link Based on Light-Emitting Diode Technology

paper_content:

1-Gbit/s transmission is demonstrated over 50 m of step-index PMMA plastic optical fiber (1-mm core-diameter) using a commercial light-emitting diode. This is enabled by use of discrete multitone modulation with up to 64-QAM constellation mapping.
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paper_title: 24-Gb/s Transmission over 730 m of Multimode Fiber by Direct Modulation of an 850-nm VCSEL using Discrete Multi-tone Modulation

paper_content:

Using discrete multi-tone modulation with up to 64-QAM mapping, 24-Gb/s transmission is experimentally demonstrated over 730 m of MMF by direct modulation of an 850-nm VCSEL and direct detection with a MMF receiver.
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paper_title: Cost-effective 33-Gbps intensity modulation direct detection multi-band OFDM LR-PON system employing a 10-GHz-based transceiver.

paper_content:

We develop a dynamic multi-band OFDM subcarrier allocation scheme to fully utilize the available bandwidth under the restriction of dispersion- and chirp-related power fading. The experimental results successfully demonstrate an intensity-modulation-direct-detection 34.78-Gbps OFDM signal transmissions over 100-km long-reach (LR) passive-optical networks (PONs) based on a cost-effective 10-GHz EAM and a 10-GHz PIN. Considering 0-100-km transmission bandwidth of a 10-GHz EAM, the narrowest bandwidth is theoretically evaluated to occur at ~40 km, instead of 100 km. Consequently, the performances of 20-100-km PONs are experimentally investigated, and at least 33-Gbps capacity is achieved to support LR-PONs of all possible 20-100-km radii.
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paper_title: Transmission performance of adaptively modulated optical OFDM signals in multimode fiber links

paper_content:

A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) is proposed and numerical simulations of the transmission performance of AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback lasers (DMLs). It is shown that 28 Gb/s intensity modulation and direct-detection AMOOFDM signal transmission over 300-m MMFs is feasible in unamplified DML-based links having 3-dB bandwidths of 150MHz/km. In addition, AMOOFDM is less susceptible to modal dispersion and variation in launching conditions when compared with existing schemes.
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paper_title: No-Guard-Interval Coherent Optical OFDM for 100-Gb/s Long-Haul WDM Transmission

paper_content:

This paper describes coherent optical orthogonal frequency division multiplexing (CO-OFDM) techniques for the long-haul transmission of 100-Gb/s-class channels. First, we discuss the configurations of the transmitter and receiver that implement the optical multiplexing/demultiplexing techniques for high-speed CO-OFDM transmission. Next, we review the no-guard-interval (No-GI) CO-OFDM transmission scheme which utilizes optical multiplexing for OFDM signal generation and the intradyne receiver configuration with digital signal processing (DSP). We examine the transmission characteristics of the proposed scheme, and show that No-GI CO-OFDM offers compact signal spectra and superior performance with regard to tolerance against optical amplifier noise and polarization-mode dispersion (PMD). We then introduce long-haul high-capacity transmission experiments employing No-GI CO-OFDM; 13.4 Tb/s (134 times 111 Gb/s) transmission is successfully demonstrated over 3600 km of ITU-T G.652 single-mode fiber without using optical dispersion compensation.
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paper_title: Adaptive Optical Wireless OFDM System with Controlled Asymmetric Clipping

paper_content:

Optical wireless (OW) technology is attractive for short-range high-speed transmission, especially in RF sensitive environments or where secure applications are desired. We consider transmission over a broadband OW channel, present in the non-directed line-of-sight (LOS) link. For communication, we assume a system concept based on a modulation-adaptive OFDM (DMT). Such system offers efficient channel capacity exploitation, while avoiding inconvenient pointing and tracking mechanisms. Moreover, it allows deployment of simple optical components and efficient electrical signal processing. We first show that the dynamically adaptive system can provide great transmission rate enhancements compared to the statically designed one, even assuming a very conservative constraint on the electrical signal waveform (i.e., no clipping). Then, we show that significant further improvements can be achieved by tolerating some clipping, at the cost of accepting a minor increase of the symbol error rate.
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paper_title: Adaptive OFDM system for communications over the indoor wireless optical channel

paper_content:

The authors propose an adaptive orthogonal frequency division multiplexing (OFDM) system for communications over the indoor wireless diffuse optical channel. This channel can be characterised as short-term stationary, with severe attenuation and multipath-induced penalty, and high dependence on the space distribution of emitters and receivers. We have chosen OFDM systems because of their capability of supporting high data rates without channel equalisation. They also mitigate the quality of service fluctuations induced when space distribution of emitters and receivers varies. The performance of the new proposed scheme is compared with that of an adaptive system described in a previous work. The obtained results show that a significant increase of the system throughput is attained over noisy wireless optical channels.
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paper_title: OFDM for Optical Communications

paper_content:

The first book on optical OFDM by the leading pioneers in the field. The only book to cover error correction codes for optical OFDM. It gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented. It contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers. This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. 'This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view, this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks' - Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology.
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paper_title: 448-Gb/s Reduced-Guard-Interval CO-OFDM Transmission Over 2000 km of Ultra-Large-Area Fiber and Five 80-GHz-Grid ROADMs

paper_content:

We propose a novel coherent optical orthogonal frequency-division multiplexing (CO-OFDM) scheme with reduced guard interval (RGI) for high-speed high-spectral-efficiency long-haul optical transmission. In this scheme, fiber chromatic dispersion is compensated for within the receiver rather than being accommodated by the guard interval (GI) as in conventional CO-OFDM, thereby reducing the needed GI, especially when fiber dispersion is large. We demonstrate the generation of a 448-Gb/s RGI-CO-OFDM signal with 16-QAM subcarrier modulation through orthogonal band multiplexing. This signal occupies an optical bandwidth of 60 GHz, and is transmitted over 2000 km of ultra-large-area fiber (ULAF) with five passes through an 80-GHz-grid wavelength-selective switch. Banded digital coherent detection with two detection bands is used to receive this 448-Gb/s signal. Wavelength-division multiplexed transmission of three 80-GHz spaced 448-Gb/s RGI-CO-OFDM channels is also demonstrated, achieving a net system spectral efficiency of 5.2 b/s/Hz and a transmission distance of 1600 km of ULAF.
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paper_title: Coherent optical OFDM: theory and design.

paper_content:

Coherent optical OFDM (CO-OFDM) has recently been proposed and the proof-of-concept transmission experiments have shown its extreme robustness against chromatic dispersion and polarization mode dispersion. In this paper, we first review the theoretical fundamentals for CO-OFDM and its channel model in a 2x2 MIMO-OFDM representation. We then present various design choices for CO-OFDM systems and perform the nonlinearity analysis for RF-to-optical up-converter. We also show the receiver-based digital signal processing to mitigate self-phase-modulation (SPM) and Gordon-Mollenauer phase noise, which is equivalent to the midspan phase conjugation.
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paper_title: 10x121.9-Gb/s PDM-OFDM Transmission with 2-b/s/Hz Spectral Efficiency over 1,000 km of SSMF

paper_content:

PDM-OFDM transmission of 10x121.9-Gb/s (112.6-Gb/s without OFDM overhead) at 50-GHz channel spacing is demonstrated over 1,000-km SSMF without any inline dispersion compensation. 8-QAM subcarrier modulation allows transmission of 121.9 Gb/s within a 22.8-GHz optical bandwidth.
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paper_title: Zero-guard-interval coherent optical OFDM with overlapped frequency-domain CD and PMD equalization

paper_content:

This paper presents a new channel estimation/equalization algorithm for coherent OFDM (CO-OFDM) digital receivers, which enables the elimination of the cyclic prefix (CP) for OFDM transmission. We term this new system as the zero-guard-interval (ZGI)-CO-OFDM. ZGI-CO-OFDM employs an overlapped frequency-domain equalizer (OFDE) to compensate both chromatic dispersion (CD) and polarization mode dispersion (PMD) before the OFDM demodulation. Despite the zero CP overhead, ZGI-CO-OFDM demonstrates a superior PMD tolerance than the previous reduced-GI (RGI)-CO-OFDM, which is verified under several different PMD conditions. Additionally, ZGI-CO-OFDM can improve the channel estimation accuracy under high PMD conditions by using a larger intra-symbol frequency-averaging (ISFA) length as compared to RGI-CO-OFDM. ZGI-CO-OFDM also enables the use of ever smaller fast Fourier transform (FFT) sizes (i.e. <128), while maintaining the zero CP overhead. Finally, we provide an analytical comparison of the computation complexity between the conventional, RGI- and ZGI- CO-OFDM. We show that ZGI-CO-OFDM requires reasonably small additional computation effort (~13.6%) compared to RGI-CO-OFDM for 112-Gb/s transmission over a 1600-km dispersion-uncompensated optical link.
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paper_title: Orthogonal frequency division multiplexing for high-speed optical transmission

paper_content:

Optical Orthogonal frequency division multiplexing (OOFDM) is shown to outperform RZ-OOK transmission in high-speed optical communications systems in terms of transmission distance and spectral efficiency. The OOFDM in combination with the subcarrier multiplexing offers a significant improvement in spectral efficiency of at least 2.9 bits/s/Hz.
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paper_title: Optical OFDM - A Candidate for Future Long-Haul Optical Transmission Systems

paper_content:

We review coherent-optical orthogonal frequency division multiplexing (OFDM) for long-haul optical transmission systems. Two important aspects of such systems are reviewed: RF-aided phase noise compensation and polarization division multiplexing enabled by MIMO processing.
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paper_title: 121.9-Gb/s PDM-OFDM Transmission With 2-b/s/Hz Spectral Efficiency Over 1000 km of SSMF

paper_content:

We discuss optical multi-band orthogonal frequency division multiplexing (OFDM) and show that by using multiple parallel OFDM bands, the required bandwidth of the digital-to-analogue/ analogue-to-digital converters and the required cyclic prefix can significantly be reduced. With the help of four OFDM bands and polarization division multiplexing (PDM) we report continuously detectable transmission of 10 times121.9-Gb/s (112.6-Gb/s without OFDM overhead) at 50-GHz channel spacing over 1,000-km standard single mode fiber (SSMF) without any inline dispersion compensation. In this experiment 8 QAM subcarrier modulation is used which confines the spectrum of the 121.9 Gb/s PDM-OFDM signal within a 22.8 GHz optical bandwidth. Moreover, we propose a digital signal processing method to reduce the matching requirements for the wideband transmitter IQ mixer structures required for PDM-OFDM.
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paper_title: Transmission of 1.2 Tb/s continuous waveband PDM-OFDM-FDM signal with spectral efficiency of 3.3 bit/s/Hz over 400 km of SSMF

paper_content:

We demonstrate generation, transmission and reception of a 1.21 Tb/s continuous waveband PDM-OFDM-FDM signal with spectral efficiency of 3.33 bit/s/Hz. After DCF-free transmission over 400-km SSMF a considerable Q-factor margin of 2dB vs. EFEC limit was achieved.
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paper_title: Coherent optical orthogonal frequency division multiplexing

paper_content:

Coherent optical orthogonal frequency division multiplexing is proposed to combat dispersion in optical media. It is shown that optical-signal-to-noise ratio penalty at 10 Gbit/s is maintained below 2 dB for 3000 km transmission of standard-singlemode fibre without dispersion compensation.
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paper_title: 107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing.

paper_content:

Coherent optical OFDM (CO-OFDM) has emerged as an attractive modulation format for the forthcoming 100 Gb/s Ethernet. However, even the spectral-efficient implementation of CO-OFDM requires digital-to-analog converters (DAC) and analog-to-digital converters (ADC) to operate at the bandwidth which may not be available today or may not be cost-effective. In order to resolve the electronic bandwidth bottleneck associated with DAC/ADC devices, we propose and elucidate the principle of orthogonal-band-multiplexed OFDM (OBM-OFDM) to subdivide the entire OFDM spectrum into multiple orthogonal bands. With this scheme, the DAC/ADCs do not need to operate at extremely high sampling rate. The corresponding mapping to the mixed-signal integrated circuit (IC) design is also revealed. Additionally, we show the proof-of-concept transmission experiment through optical realization of OBM-OFDM. To the best of our knowledge, we present the first experimental demonstration of 107 Gb/s QPSK-encoded CO-OFDM signal transmission over 1000 km standard-single- mode-fiber (SSMF) without optical dispersion compensation and without Raman amplification. The demonstrated system employs 2x2 MIMO-OFDM signal processing and achieves high electrical spectral efficiency with direct-conversion at both transmitter and receiver.
---
paper_title: Optical orthogonal frequency division multiplexing using frequency/time domain filtering for high spectral efficiency up to 1 bit/s/Hz

paper_content:

Summary form only given. We have proposed a novel optical orthogonal frequency division multiplexing technique that can overcome the spectral efficiency limitation of the conventional WDM system. This scheme permits substantial overlapping of the spectrum and can achieve the spectral efficiency up to 1 bit/s/Hz in principle. For demultiplexing, we used a newly developed optical discrete Fourier transformer (DFT) instead of electrical digital processing, which is impossible to apply in the optical frequency range. The optical DFT was realized by using a set of delay lines, a phase shifter and a coupler in the frequency domain and bit synchronization and an optical gate in the time domain. In experimental demonstration of this scheme, error-free operation was obtained with a 0.8 bit/s/Hz of spectral efficiency.
---
paper_title: Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8 Tbit/s

paper_content:

OFDM data with line rates of 5.4 Tbit/s or 10.8 Tbit/s are generated and decoded with a new real-time all-optical FFT receiver. Each of 75 carriers of a comb source is encoded with 18 GBd QPSK or 16-QAM.
---
paper_title: No-Guard-Interval Coherent Optical OFDM for 100-Gb/s Long-Haul WDM Transmission

paper_content:

This paper describes coherent optical orthogonal frequency division multiplexing (CO-OFDM) techniques for the long-haul transmission of 100-Gb/s-class channels. First, we discuss the configurations of the transmitter and receiver that implement the optical multiplexing/demultiplexing techniques for high-speed CO-OFDM transmission. Next, we review the no-guard-interval (No-GI) CO-OFDM transmission scheme which utilizes optical multiplexing for OFDM signal generation and the intradyne receiver configuration with digital signal processing (DSP). We examine the transmission characteristics of the proposed scheme, and show that No-GI CO-OFDM offers compact signal spectra and superior performance with regard to tolerance against optical amplifier noise and polarization-mode dispersion (PMD). We then introduce long-haul high-capacity transmission experiments employing No-GI CO-OFDM; 13.4 Tb/s (134 times 111 Gb/s) transmission is successfully demonstrated over 3600 km of ITU-T G.652 single-mode fiber without using optical dispersion compensation.
---
paper_title: Orthogonal Frequency Division Multiplexing for Adaptive Dispersion Compensation in Long Haul WDM Systems

paper_content:

Simulations show orthogonal frequency division multiplexing (OFDM) with optical single sideband modulation can adaptively compensate for dispersion in 4000-km 32×10Gbps WDM SMF links with 40% spectral efficiency. OFDM requires no reverse feedback path so can compensate rapid plant variations.
---
paper_title: Spectrally Efficient Compatible Single-Sideband Modulation for OFDM Transmission With Direct Detection

paper_content:

A combination of orthogonal frequency-division multiplexing (OFDM) and compatible single-sideband modulation (CompSSB) using a standard direct-detection scheme is suggested to overcome chromatic dispersion without explicit compensation. Since the proposed type of SSB modulation does not require a spectral gap between optical carrier and subcarriers, it is highly spectrally efficient and the complexity in the analogue part is reduced compared to known direct-detection schemes for OFDM.
---
paper_title: Maximizing the Transmission Performance of Adaptively Modulated Optical OFDM Signals in Multimode-Fiber Links by Optimizing Analog-to-Digital Converters

paper_content:

Based on a comprehensive theoretical model of a recently proposed novel technique known as adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM), investigations are undertaken into the impact of an analog-to-digital converter involved in the AMOOFDM modem on the transmission performance of AMOOFDM signals in unamplified intensity-modulation and direct-detection (IMDD) multimode-fiber (MMF)-based links. It is found that signal quantization and clipping effects are significant in determining the maximum achievable transmission performance of the AMOOFDM modem. A minimum quantization bit value of ten and optimum clipping ratio of 13 dB are identified, based on which, the transmission performance is maximized. It is shown that 40-Gb/s-over-220-m and 32-Gb/s-over-300-m IMDD-AMOOFDM signal transmission at 1550 nm with loss margins of about 15 dB is feasible in the installed worst case 62.5-mum MMF links having 3-dB effective bandwidths as small as 150 MHz middot km. Meanwhile, excellent performance, robustness to fiber types, and variation in launch conditions and signal bit rates is observed. In addition, discussions are presented of the potential of 100-Gb/s AMOOFDM signal transmission over installed MMF links
---
paper_title: No-Guard-Interval Coherent Optical OFDM for 100-Gb/s Long-Haul WDM Transmission

paper_content:

This paper describes coherent optical orthogonal frequency division multiplexing (CO-OFDM) techniques for the long-haul transmission of 100-Gb/s-class channels. First, we discuss the configurations of the transmitter and receiver that implement the optical multiplexing/demultiplexing techniques for high-speed CO-OFDM transmission. Next, we review the no-guard-interval (No-GI) CO-OFDM transmission scheme which utilizes optical multiplexing for OFDM signal generation and the intradyne receiver configuration with digital signal processing (DSP). We examine the transmission characteristics of the proposed scheme, and show that No-GI CO-OFDM offers compact signal spectra and superior performance with regard to tolerance against optical amplifier noise and polarization-mode dispersion (PMD). We then introduce long-haul high-capacity transmission experiments employing No-GI CO-OFDM; 13.4 Tb/s (134 times 111 Gb/s) transmission is successfully demonstrated over 3600 km of ITU-T G.652 single-mode fiber without using optical dispersion compensation.
---
paper_title: Coherent optical orthogonal frequency division multiplexing

paper_content:

Coherent optical orthogonal frequency division multiplexing is proposed to combat dispersion in optical media. It is shown that optical-signal-to-noise ratio penalty at 10 Gbit/s is maintained below 2 dB for 3000 km transmission of standard-singlemode fibre without dispersion compensation.
---
paper_title: MIMO systems with antenna selection

paper_content:

Multiple-input-multiple-output (MIMO) wireless systems are those that have multiple antenna elements at both the transmitter and receiver. They were first investigated by computer simulations in the 1980s. Since that time, interest in MIMO systems has exploded. They are now being used for third-generation cellular systems (W-CDMA) and are discussed for future high-performance modes of the highly successful IEEE 802.11 standard for wireless local area networks. MIMO-related topics also occupy a considerable part of today's academic communications research. The multiple antennas in MIMO systems can be exploited in two different ways. One is the creation of a highly effective antenna diversity system; the other is the use of the multiple antennas for the transmission of several parallel data streams to increase the capacity of the system. This article presented an overview of MIMO systems with antenna selection. The transmitter, the receiver, or both use only the signals from a subset of the available antennas. This allows considerable reductions in the hardware expense.
---
paper_title: PMD-Supported Coherent Optical OFDM Systems

paper_content:

Although polarization-mode dispersion (PMD) greatly impairs conventional high-speed single-carrier systems, it is shown that for multicarrier systems such as coherent optical orthogonal frequency-division-multiplexed systems (CO-OFDM), not only does PMD not cause any impairment, but it also provides a benefit of polarization diversity against polarization-dependent-loss-induced fading and consequently improves the system margin. The PMD benefit to fiber nonlinearity reduction in CO-OFDM systems is also predicted
---
paper_title: OFDM for Optical Communications

paper_content:

The first book on optical OFDM by the leading pioneers in the field. The only book to cover error correction codes for optical OFDM. It gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented. It contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers. This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. 'This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view, this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks' - Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology.
---
paper_title: OFDM for Flexible High-Speed Optical Networks

paper_content:

Fast advancing silicon technology underpinned by Moore's law is creating a major transformation in optical fiber communications. The recent upsurge of interests in optical orthogonal frequency-division multiplexing (OFDM) as an efficient modulation and multiplexing scheme is merely a manifestation of this unmistakable trend. Since the formulation of the fundamental concept of OFDM by Chang in 1966 and many landmark works by others thereafter, OFDM has been triumphant in almost all the major RF communication standards. Nevertheless, its application to optical communications is rather nascent and its potential success in the optical domain remains an open question. This tutorial provides a review of optical OFDM slanted towards emerging optical fiber networks. The objective of the tutorial is two-fold: (i) to review OFDM fundamentals from its basic mathematical formation to its salient disadvantages and advantages, and (ii) to reveal the unique characteristics of the fiber optical channel and identify the challenges and opportunities in the application of optical OFDM.
---
paper_title: Bit and Power Loading for Coherent Optical OFDM

paper_content:

We show the first experiment of bit and power loading for coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) systems. The data rate of CO-OFDM systems can be dynamically adjusted according to the channel condition. The system performance can be further improved through optimal power loading into each modulation band.
---
paper_title: Transparent WDM network with bitrate tunable optical OFDM transponders

paper_content:

Reach estimations for several variable-bitrate OFDM schemes are presented and discussed in the framework of a transparent EU core network scenario. 44% reduction on OE interfaces is found compared to a fixed-bitrate 40Gb/s network.
---
paper_title: Optical Network Design With Mixed Line Rates and Multiple Modulation Formats

paper_content:

With the growth of traffic volume and the emergence of various new applications, future telecom networks are expected to be increasingly heterogeneous with respect to applications supported and underlying technologies employed. To address this heterogeneity, it may be most cost effective to set up different lightpaths at different bit rates in such a backbone telecom mesh network employing optical wavelength-division multiplexing. This approach can be cost effective because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths), while a high-bit-rate service can be accommodated directly on a wavelength itself. Optical networks with mixed line rates (MLRs), e.g., 10/40/100 Gb/s over different wavelength channels, are a new networking paradigm. The unregenerated reach of a lightpath depends on its line rate. So, the assignment of a line rate to a lightpath is a tradeoff between its capacity and transparent reach. Thus, based on their signal-quality constraints (threshold bit error rate), intelligent assignment of line rates to lightpaths can minimize the need for signal regeneration. This constraint on the transparent reach based on threshold signal quality can be relaxed by employing more advanced modulation formats, but with more investment. We propose a design method for MLR optical networks with transceivers employing different modulation formats. Our results demonstrate the tradeoff between a transceiver's cost and its optical reach in overall network design.
---
paper_title: Defragmentation of transparent Flexible optical WDM (FWDM) networks

paper_content:

We introduce the network defragmentation problem for FWDM networks, formulate it, and propose heuristics. The network defragmentation process consolidates the available spectrum significantly while minimizing the number of interrupted connections.
---
paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
---
paper_title: On the spectrum-efficiency of bandwidth-variable optical OFDM transport networks

paper_content:

We investigated the high spectrum efficiency property of the bandwidth-variable optical OFDM (BV-OOFDM) transport networks. In contrast to mixed-line-rate (MLR) networks, BV-OOFDM enables flexible allocation and efficient utilization of the spectral resource.
---
paper_title: Elastic optical networks with 25–100G format-versatile WDM transmission systems

paper_content:

We propose a network model based on format-versatile transceiver for data-rate tunability. We estimate each format's resistance to degradations and dimension a backbone network accordingly, yielding 20% savings on resources compared to single-rate networks.
---
paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
---
paper_title: Routing, Wavelength Assignment, and Spectrum Allocation in Transparent Flexible Optical WDM (FWDM) Networks

paper_content:

We propose the flexible optical WDM network architecture, and introduce the routing, wavelength assignment, and spectrum allocation problem in transparent FWDM networks. Spectrum and cost efficiency are improved compared to fixed grid networks.
---
paper_title: Elastic optical networks with 25–100G format-versatile WDM transmission systems

paper_content:

We propose a network model based on format-versatile transceiver for data-rate tunability. We estimate each format's resistance to degradations and dimension a backbone network accordingly, yielding 20% savings on resources compared to single-rate networks.
---
paper_title: Optical Network Design With Mixed Line Rates and Multiple Modulation Formats

paper_content:

With the growth of traffic volume and the emergence of various new applications, future telecom networks are expected to be increasingly heterogeneous with respect to applications supported and underlying technologies employed. To address this heterogeneity, it may be most cost effective to set up different lightpaths at different bit rates in such a backbone telecom mesh network employing optical wavelength-division multiplexing. This approach can be cost effective because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths), while a high-bit-rate service can be accommodated directly on a wavelength itself. Optical networks with mixed line rates (MLRs), e.g., 10/40/100 Gb/s over different wavelength channels, are a new networking paradigm. The unregenerated reach of a lightpath depends on its line rate. So, the assignment of a line rate to a lightpath is a tradeoff between its capacity and transparent reach. Thus, based on their signal-quality constraints (threshold bit error rate), intelligent assignment of line rates to lightpaths can minimize the need for signal regeneration. This constraint on the transparent reach based on threshold signal quality can be relaxed by employing more advanced modulation formats, but with more investment. We propose a design method for MLR optical networks with transceivers employing different modulation formats. Our results demonstrate the tradeoff between a transceiver's cost and its optical reach in overall network design.
---
paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
---
paper_title: Spectrally/bitrate flexible optical network planning

paper_content:

We consider the Routing and Spectrum Allocation (RSA) problem in an OFDM-based optical network with elastic bandwidth allocation. We asses the spectrum utilization gains of this flexible architecture compared to a traditional fixed-grid rigid-bandwidth WDM network.
---
paper_title: PONIARD: A Programmable Optical Networking Infrastructure for Advanced Research and Development of Future Internet

paper_content:

Motivated by the design goals of Global Environment for Network Innovation (GENI), we consider how to support the slicing of link bandwidth resources as well as the virtualization of optical access networks and optical backbone mesh networks. Specifically, in this paper, we study a novel programmable mechanism called optical orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) for link virtualization. Unlike conventional time division multiplexing (TDM)/time division multiple access (TDMA) and wavelength division multiplexing (WDM)/wavelength division multiple access (WDMA) methods, optical OFDM/OFDMA utilizes advanced digital signal processing (DSP), parallel signal detection (PSD), and flexible resource management schemes for subwavelength level multiplexing and grooming. Simulations as well as experiments are conducted to demonstrate performance improvements and system benefits including cost-reduction and service transparency.
---
paper_title: Demonstration of novel spectrum-efficient elastic optical path network with per-channel variable capacity of 40 Gb/s to over 400 Gb/s

paper_content:

We demonstrated, for the first time, a novel spectrum-efficient elastic optical path network for 100 Gb/s services and beyond, based on flexible rate transceivers and variable-bandwidth wavelength crossconnects.
---
paper_title: Bit-rate-flexible all-optical OFDM transceiver using variable multi-carrier source and DQPSK/DPSK mixed multiplexing

paper_content:

We propose and demonstrate a bit-rate-flexible all-optical OFDM transceiver. Signals were successfully generated at 107, 42.8, 32.1, and 10.7Gbit/s and received through the transceiver. The 107-Gbit/s signal was successfully transmitted over 40-km-SMF without dispersion compensation.
---
paper_title: Transparent WDM network with bitrate tunable optical OFDM transponders

paper_content:

Reach estimations for several variable-bitrate OFDM schemes are presented and discussed in the framework of a transparent EU core network scenario. 44% reduction on OE interfaces is found compared to a fixed-bitrate 40Gb/s network.
---
paper_title: Elastic optical networks with 25–100G format-versatile WDM transmission systems

paper_content:

We propose a network model based on format-versatile transceiver for data-rate tunability. We estimate each format's resistance to degradations and dimension a backbone network accordingly, yielding 20% savings on resources compared to single-rate networks.
---
paper_title: Bit and Power Loading for Coherent Optical OFDM

paper_content:

We show the first experiment of bit and power loading for coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) systems. The data rate of CO-OFDM systems can be dynamically adjusted according to the channel condition. The system performance can be further improved through optimal power loading into each modulation band.
---
paper_title: Flexible-bandwidth and format-agile networking based on optical arbitrary waveform generation and wavelength selective switches

paper_content:

This paper experimentally demonstrates flexible-bandwidth networking by splitting a 500-GHz waveform generated by optical arbitrary waveform generation into its two tributary spectral slices using a liquid-crystal spatial light phase modulator as a wavelength selective switch.
---
paper_title: Distance-adaptive super-wavelength routing in elastic optical path network (SLICE) with optical OFDM

paper_content:

We propose a spectrally-efficient super-wavelength-path routing in SLICE by selecting a set of subcarrier numbers and modulation levels according to path distances. We demonstrate 420 Gb/s path routing using short-reach 14-subcarrier 8-APSK and long-reach 21-subcarrier QPSK.
---
paper_title: Bandwidth scalable, coherent transmitter based on parallel synthesis of multiple spectral slices

paper_content:

This paper presents a bandwidth-scalable, coherent optical transmitter based on the parallel synthesis of multiple spectral slices. As a proof-of-principle, two spectral slice, 6-ns DPSK and QPSK waveforms at 12 Gsymbols/s are generated and measured.
---
paper_title: Experimental demonstration of 400 Gb/s multi-flow, multi-rate, multi-reach optical transmitter for efficient elastic spectral routing

paper_content:

We demonstrate a multi-flow/multi-rate/multi-reach optical transmitter and spectral routing of total 400 Gb/s optical flows. The number of optical flows, bit rate, and optical reach can be adjusted to enable efficient elastic spectral routing.
---
paper_title: Optical Path Aggregation for 1-Tb/s Transmission in Spectrum-Sliced Elastic Optical Path Network

paper_content:

We propose and experimentally demonstrate optical path aggregation in a spectrum-sliced elastic optical path network (SLICE). Multiple optical orthogonal frequency-division-multiplexed (OFDM) 100-Gb/s optical paths are aggregated in the optical domain to form a spectrally continuous 1-Tb/s super-wavelength optical path and transmitted over a network of bandwidth-variable wavelength cross-connects. We evaluate the potential implementation issues and conclude that the OFDM paths can be optically aggregated with optical signal-to-noise ratio penalty of less than 1 dB.
---
paper_title: Bit and Power Loading for Coherent Optical OFDM

paper_content:

We show the first experiment of bit and power loading for coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) systems. The data rate of CO-OFDM systems can be dynamically adjusted according to the channel condition. The system performance can be further improved through optimal power loading into each modulation band.
---
paper_title: Highly programmable wavelength selective switch based on liquid crystal on silicon switching elements

paper_content:

We present a novel wavelength selective switch (WSS) based on a liquid crystal on silicon (LCOS) switching element. The unit operates simultaneously at both 50 and 100 GHz channel spacing and is compatible with 40 G transmission requirements.
---
paper_title: Flexible and grid-less wavelength selective switch using LCOS technology

paper_content:

The increasing spectral efficiency of Optical Transmission systems is constrained by the limitations of wavelength switching and is driving a requirement for significantly more flexible approaches to routing of the optical traffic. We present the intrinsic Grid-free capabilities of LCOS and show how it can be used practically in a flexible Grid architecture to maximize total fiber capacity.
---
paper_title: Experimental demonstration of a gridless multi-granular optical network supporting flexible spectrum switching

paper_content:

A gridless dynamic multi-granular optical network supporting flexible spectrum allocation is proposed and experimentally demonstrated to efficiently accommodate high-speed traffic and increase channel density for lower speed traffic leading to improved network efficiency and scalability.
---
paper_title: Wavelength-Selective Switches for ROADM Applications

paper_content:

The trends, architecture, and performance of wavelength-selective switches (WSS) are analyzed in the context of their application to reconfigurable optical add/drop multiplexer (ROADM)-based optical networks. The resulting analyses define the requirements for the latest generation of ROADM systems and provide insight into the critical specifications of this technology. In addition, the current trends for WSS technology are reviewed in the context of synergies with the strengths of different switching technologies.
---
paper_title: Data rate and channel spacing flexible wavelength blocking filter

paper_content:

We present a high-resolution blocking filter, which seamlessly supports data rates from 2.5 Gbit/s to 160 Gbit/s with a granularity of 13.2 GHz. The filter consists of a linear array of 64 MEMS micromirrors and a high-dispersion echelle grating.
---
paper_title: Simple all-optical FFT scheme enabling Tbit/s real-time signal processing

paper_content:

A practical scheme to perform the fast Fourier transform in the optical domain is introduced. Optical real-time FFT signal processing is performed at speeds far beyond the limits of electronic digital processing, and with negligible energy consumption. To illustrate the power of the method we demonstrate an optical 400 Gbit/s OFDM receiver. It performs an optical real-time FFT on the consolidated OFDM data stream, thereby demultiplexing the signal into lower bit rate subcarrier tributaries, which can then be processed electronically.
---
paper_title: Wavelength blocking filter with flexible data rates and channel spacing

paper_content:

This work presents a high-resolution (13.2 GHz) channel-blocking optical filter, suitable for use as a reconfigurable optical add/drop multiplexer (ROADM), which seamlessly supports data rates from 2.5 to 160 Gb/s. The filter consists of a linear array of 64 MEMS micromirrors and a high-dispersion echelle grating. The demonstrated device had an insertion loss of 9 dB, a loss ripple of 1.2 dB, and a group delay ripple of 15 ps. Data transmission through the device with various mixed data rate scenarios ranging from 2.5 to 160 Gb/s showed negligible penalty, except at 40 Gb/s where a maximum penalty of 1.5 dB was observed due to a phase coherence with the blocker filter ripple.
---
paper_title: Demonstration of novel spectrum-efficient elastic optical path network with per-channel variable capacity of 40 Gb/s to over 400 Gb/s

paper_content:

We demonstrated, for the first time, a novel spectrum-efficient elastic optical path network for 100 Gb/s services and beyond, based on flexible rate transceivers and variable-bandwidth wavelength crossconnects.
---
paper_title: Demonstration of bit rate variable ROADM functionality on an optical OFDM superchannel

paper_content:

We demonstrate a bit rate variable add- and drop function performed on an optical OFDM superchannel signal by optical filtering and superposition of OFDM subbands and the application of different modulation formats for dynamic networks.
---
paper_title: Data rate and channel spacing flexible wavelength blocking filter

paper_content:

We present a high-resolution blocking filter, which seamlessly supports data rates from 2.5 Gbit/s to 160 Gbit/s with a granularity of 13.2 GHz. The filter consists of a linear array of 64 MEMS micromirrors and a high-dispersion echelle grating.
---
paper_title: Highly programmable wavelength selective switch based on liquid crystal on silicon switching elements

paper_content:

We present a novel wavelength selective switch (WSS) based on a liquid crystal on silicon (LCOS) switching element. The unit operates simultaneously at both 50 and 100 GHz channel spacing and is compatible with 40 G transmission requirements.
---
paper_title: Flexible and grid-less wavelength selective switch using LCOS technology

paper_content:

The increasing spectral efficiency of Optical Transmission systems is constrained by the limitations of wavelength switching and is driving a requirement for significantly more flexible approaches to routing of the optical traffic. We present the intrinsic Grid-free capabilities of LCOS and show how it can be used practically in a flexible Grid architecture to maximize total fiber capacity.
---
paper_title: Filtering characteristics of highly-spectrum efficient spectrum-sliced elastic optical path (SLICE) network

paper_content:

We investigate the performance of OFDM-modulated signals in spectrum-sliced elastic optical path network. We analyze the filtering characteristics and the guard band for multi-node transmission. The architecture increases spectral efficiency over the current WDM systems.
---
paper_title: Experimental demonstration of a gridless multi-granular optical network supporting flexible spectrum switching

paper_content:

A gridless dynamic multi-granular optical network supporting flexible spectrum allocation is proposed and experimentally demonstrated to efficiently accommodate high-speed traffic and increase channel density for lower speed traffic leading to improved network efficiency and scalability.
---
paper_title: Demonstration of novel spectrum-efficient elastic optical path network with per-channel variable capacity of 40 Gb/s to over 400 Gb/s

paper_content:

We demonstrated, for the first time, a novel spectrum-efficient elastic optical path network for 100 Gb/s services and beyond, based on flexible rate transceivers and variable-bandwidth wavelength crossconnects.
---
paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
---
paper_title: Experimental demonstration of a gridless multi-granular optical network supporting flexible spectrum switching

paper_content:

A gridless dynamic multi-granular optical network supporting flexible spectrum allocation is proposed and experimentally demonstrated to efficiently accommodate high-speed traffic and increase channel density for lower speed traffic leading to improved network efficiency and scalability.
---
paper_title: Wavelength-Selective Switches for ROADM Applications

paper_content:

The trends, architecture, and performance of wavelength-selective switches (WSS) are analyzed in the context of their application to reconfigurable optical add/drop multiplexer (ROADM)-based optical networks. The resulting analyses define the requirements for the latest generation of ROADM systems and provide insight into the critical specifications of this technology. In addition, the current trends for WSS technology are reviewed in the context of synergies with the strengths of different switching technologies.
---
paper_title: Dynamic routing and frequency slot assignment for elastic optical path networks that adopt distance adaptive modulation

paper_content:

We propose a dynamic routing and frequency slot assignment algorithm for SLICE networks that employ distance adaptive modulation. We verify that the spectrum utilization penalty that stems from non-uniform bandwidth allocation is marginal.
---
paper_title: Routing and Spectrum Allocation in OFDM-Based Optical Networks with Elastic Bandwidth Allocation

paper_content:

Orthogonal Frequency Division Multiplexing (OFDM) has been recently proposed as a modulation technique for optical networks, due to its good spectral efficiency and impairment tolerance. Optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions. We consider the planning problem of an OFDM-based optical network where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers. We introduce the Routing and Spectrum Allocation (RSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, and present various algorithms to solve the RSA. We start by presenting an optimal ILP RSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RSA into two substituent subproblems, namely, (i) routing and (ii) spectrum allocation (R+SA) and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all traffic matrix connections. To feed the sequential algorithm, two ordering policies are proposed; a simulated annealing meta-heuristic is also used to obtain even better orderings. Our results indicate that the proposed sequential heuristic with appropriate ordering yields close to optimal solutions in low running times.
---
paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
---
paper_title: Defragmentation of transparent Flexible optical WDM (FWDM) networks

paper_content:

We introduce the network defragmentation problem for FWDM networks, formulate it, and propose heuristics. The network defragmentation process consolidates the available spectrum significantly while minimizing the number of interrupted connections.
---
paper_title: Routing and Spectrum Allocation in OFDM-Based Optical Networks with Elastic Bandwidth Allocation

paper_content:

Orthogonal Frequency Division Multiplexing (OFDM) has been recently proposed as a modulation technique for optical networks, due to its good spectral efficiency and impairment tolerance. Optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions. We consider the planning problem of an OFDM-based optical network where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers. We introduce the Routing and Spectrum Allocation (RSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, and present various algorithms to solve the RSA. We start by presenting an optimal ILP RSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RSA into two substituent subproblems, namely, (i) routing and (ii) spectrum allocation (R+SA) and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all traffic matrix connections. To feed the sequential algorithm, two ordering policies are proposed; a simulated annealing meta-heuristic is also used to obtain even better orderings. Our results indicate that the proposed sequential heuristic with appropriate ordering yields close to optimal solutions in low running times.
---
paper_title: Dynamic routing and frequency slot assignment for elastic optical path networks that adopt distance adaptive modulation

paper_content:

We propose a dynamic routing and frequency slot assignment algorithm for SLICE networks that employ distance adaptive modulation. We verify that the spectrum utilization penalty that stems from non-uniform bandwidth allocation is marginal.
---
paper_title: Routing and Spectrum Allocation in OFDM-Based Optical Networks with Elastic Bandwidth Allocation

paper_content:

Orthogonal Frequency Division Multiplexing (OFDM) has been recently proposed as a modulation technique for optical networks, due to its good spectral efficiency and impairment tolerance. Optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions. We consider the planning problem of an OFDM-based optical network where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers. We introduce the Routing and Spectrum Allocation (RSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, and present various algorithms to solve the RSA. We start by presenting an optimal ILP RSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RSA into two substituent subproblems, namely, (i) routing and (ii) spectrum allocation (R+SA) and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all traffic matrix connections. To feed the sequential algorithm, two ordering policies are proposed; a simulated annealing meta-heuristic is also used to obtain even better orderings. Our results indicate that the proposed sequential heuristic with appropriate ordering yields close to optimal solutions in low running times.
---
paper_title: Dynamic routing and spectrum assignment in flexible optical path networks

paper_content:

We propose dynamic routing and spectrum assignment algorithms for bitrate-flexible lightpaths in OFDM-based optical networks. The novel algorithms enable dynamic spectrum assignment with more efficient resource utilization and less traffic blockings.
---
paper_title: Impact of transparent network constraints on capacity gain of elastic channel spacing

paper_content:

We compare fixed-grid network architectures with variable-spacing OFDM based solutions. We show that capacity gains can reach up to 50% but are strongly affected by physical and topological constraints of transparent networks and traffic statistics.
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paper_title: Distance-adaptive super-wavelength routing in elastic optical path network (SLICE) with optical OFDM

paper_content:

We propose a spectrally-efficient super-wavelength-path routing in SLICE by selecting a set of subcarrier numbers and modulation levels according to path distances. We demonstrate 420 Gb/s path routing using short-reach 14-subcarrier 8-APSK and long-reach 21-subcarrier QPSK.
---
paper_title: Spectrally/bitrate flexible optical network planning

paper_content:

We consider the Routing and Spectrum Allocation (RSA) problem in an OFDM-based optical network with elastic bandwidth allocation. We asses the spectrum utilization gains of this flexible architecture compared to a traditional fixed-grid rigid-bandwidth WDM network.
---
paper_title: Elastic Bandwidth Allocation in Flexible OFDM-Based Optical Networks

paper_content:

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique for optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments. We consider the planning problem of an OFDM optical network, where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers and choosing an appropriate modulation level, taking into account the transmission distance. We introduce the Routing, Modulation Level and Spectrum Allocation (RMLSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, prove that is also NP-complete and present various algorithms to solve it. We start by presenting an optimal ILP RMLSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RMLSA into its two substituent subproblems, namely 1) routing and modulation level and 2) spectrum allocation (RML+SA), and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all the connections in the traffic matrix. In the sequential algorithm, we investigate two policies for defining the order in which connections are considered. We also use a simulated annealing meta-heuristic to obtain even better orderings. We examine the performance of the proposed algorithms through simulation experiments and evaluate the spectrum utilization benefits that can be obtained by utilizing OFDM elastic bandwidth allocation, when compared to a traditional WDM network.
---
paper_title: Distance-adaptive spectrum allocation in elastic optical path network (SLICE) with bit per symbol adjustment

paper_content:

We present a concept of spectrally-efficient optical networking with distance-adaptive spectral allocation by adjusting the number of modulation levels. We demonstrate it by routing 40 Gb/s optical paths using short-reach, narrow-spectrum 16APSK and long-reach QPSK.
---
paper_title: A quick method for finding shortest pairs of disjoint paths

paper_content:

Let G be a directed graph containing n vertices, one of which is a distinguished source s, and m edges, each with a non-negative cost. We consider the problem of finding, for each possible sink vertex v, a pair of edge-disjoint paths from s to v of minimum total edge cost. Suurballe has given an O(n2 logn)-time algorithm for this problem. We give an implementation of Suurballe's algorithm that runs in O(m log(1+ m/n)n) time and O(m) space. Our algorithm builds an implicit representation of the n pairs of paths; given this representation, the time necessary to explicitly construct the pair of paths for any given sink is O(1) per edge on the paths.
---
paper_title: Algorithms for maximizing spectrum efficiency in elastic optical path networks that adopt distance adaptive modulation

paper_content:

We propose optical path routing and frequency slot assignment algorithms that suit elastic optical paths and the distance adaptive modulation scheme. The algorithms are proven to yield high spectrum efficiency for the distant-adaptive frequency allocation scheme.
---
paper_title: Survivable transparent Flexible optical WDM (FWDM) networks

paper_content:

We propose an efficient survivable FWDM network design algorithm for the first time. Survivable FWDM networks are efficient in terms of spectral utilization, power consumption, and cost compared to the conventional survivable fixed grid networks.
---
paper_title: Mobipack: optimal hitless SONET defragmentation in near-optimal cost

paper_content:

We study the problem of bandwidth fragmentation in links that comprise rings and meshes in SONET networks. Fragmentation is a serious challenge for network operators since it creates "holes" in the transport pipe causing new demands to be rejected, in spite of sufficient bandwidth being available. Unlike the well-studied, general fragmentation problem, link defragmentation is "hard" and novel due to some unique constraints imposed by the SONET standard. Since a defragmentation operation typically occurs on a network carrying live traffic, in addition to the "quality" of the output, any link defragmentation algorithm has to avoid traffic hit and also optimize the "cost" of reorganizing circuits. We propose an algorithm called mobipack that is optimal in its defragmentation quality. Moreover, we demonstrate via extensive simulations, that it also achieves its goal in a hitless manner with only marginal additional cost over the optimal, making it extremely attractive to use in practice
---
paper_title: Routing and Spectrum Allocation in OFDM-Based Optical Networks with Elastic Bandwidth Allocation

paper_content:

Orthogonal Frequency Division Multiplexing (OFDM) has been recently proposed as a modulation technique for optical networks, due to its good spectral efficiency and impairment tolerance. Optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions. We consider the planning problem of an OFDM-based optical network where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers. We introduce the Routing and Spectrum Allocation (RSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, and present various algorithms to solve the RSA. We start by presenting an optimal ILP RSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RSA into two substituent subproblems, namely, (i) routing and (ii) spectrum allocation (R+SA) and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all traffic matrix connections. To feed the sequential algorithm, two ordering policies are proposed; a simulated annealing meta-heuristic is also used to obtain even better orderings. Our results indicate that the proposed sequential heuristic with appropriate ordering yields close to optimal solutions in low running times.
---
paper_title: Dynamic bandwidth allocation in flexible OFDM-based networks

paper_content:

We propose a general policy to allocate subcarriers to time-varying traffic in a flexible OFDM optical network. We compare the OFDM network performance to that of a fixed-grid WDM network using simulations.
---
paper_title: Defragmentation of transparent Flexible optical WDM (FWDM) networks

paper_content:

We introduce the network defragmentation problem for FWDM networks, formulate it, and propose heuristics. The network defragmentation process consolidates the available spectrum significantly while minimizing the number of interrupted connections.
---
paper_title: Traffic grooming in Spectrum-Elastic Optical Path Networks

paper_content:

We propose a novel approach of traffic grooming in Spectrum-Elastic Optical Path Networks. Higher spectrum efficiency is achieved by our approach comparing with non-traffic-grooming scenario.
---
paper_title: Highly survivable restoration scheme employing optical bandwidth squeezing in spectrum-sliced elastic optical path (SLICE) network

paper_content:

This paper proposes a novel restoration scheme in the spectrum-sliced elastic optical network. The proposed scheme achieves a high level of survivability for the traffic that is subject to the committed service profile.
---
paper_title: PONIARD: A Programmable Optical Networking Infrastructure for Advanced Research and Development of Future Internet

paper_content:

Motivated by the design goals of Global Environment for Network Innovation (GENI), we consider how to support the slicing of link bandwidth resources as well as the virtualization of optical access networks and optical backbone mesh networks. Specifically, in this paper, we study a novel programmable mechanism called optical orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) for link virtualization. Unlike conventional time division multiplexing (TDM)/time division multiple access (TDMA) and wavelength division multiplexing (WDM)/wavelength division multiple access (WDMA) methods, optical OFDM/OFDMA utilizes advanced digital signal processing (DSP), parallel signal detection (PSD), and flexible resource management schemes for subwavelength level multiplexing and grooming. Simulations as well as experiments are conducted to demonstrate performance improvements and system benefits including cost-reduction and service transparency.
---
paper_title: Adaptive IP/optical OFDM networking design

paper_content:

A new networking approach based on IP/optical OFDM technologies is proposed, providing an adaptive mechanism of bandwidth provisioning and pipe resizing for dynamic traffic flows. A comparison study is presented to demonstrate its advantages.
---
paper_title: Virtualized optical network (VON) for agile cloud computing environment

paper_content:

A virtualized optical network is proposed as a key to implementing increased agility and flexibility into a cloud computing environment by providing any-to-any connectivity with the appropriate optical bandwidth at the appropriate time.
---
paper_title: A programmable router interface supporting link virtualization with adaptive optical OFDMA transmission

paper_content:

A new programmable router interface with adaptive packet over optical OFDMA transmission is proposed, providing a perfect mechanism of bandwidth partition for link virtualization. A comparison study is presented to demonstrate its advantages.
---
paper_title: Energy-efficient global networks and their implications

paper_content:

Nowadays, energy related problems are becoming a key environmental, social and political issue because the demand for energy and power resources grows continuously. A decoupling of economic growth and energy consumption becomes a very important goal that can be achieved only by increasing the energy efficiency of new technologies and processes, i.e., the ability to provide a higher performance by consuming less energy. Communication networks play a significant role as the crucial part of the information and communication technologies. An adequate and future-ready communication network infrastructure has become one of the most important strategic goals of any government, region, and municipality, because a high-capacity and efficient network leads to an accelerated development of both business and society. This paper aims to give an overview on possible potentials of new technologies for implementing energy-efficient network elements. It identifies main energy-related issues in high-performance network elements and tries to draw attention to some promising approaches for implementing low-consuming components and networks. Various aspects related to applications and services that can make use of the energy-efficient and high-performance global networks are discussed. Some thoughts about possible implications on energy productivity, economy, and society can also be found.
---
paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
---
paper_title: Highly survivable restoration scheme employing optical bandwidth squeezing in spectrum-sliced elastic optical path (SLICE) network

paper_content:

This paper proposes a novel restoration scheme in the spectrum-sliced elastic optical network. The proposed scheme achieves a high level of survivability for the traffic that is subject to the committed service profile.
---

Title: A Survey on OFDM-Based Elastic Core Optical Networking

Section 1: Introduction 
Description 1: Introduce the rapid growth of Internet traffic and the need for large-capacity optical fiber transmission systems, and overview the challenges and requirements for future optical networks.

Section 2: OFDM Principle
Description 2: Explain the basic principles of OFDM technology, including its operation, advantages, and the core components of an OFDM system.

Section 3: Building Blocks of OFDM Systems
Description 3: Describe the key building blocks of an OFDM system, detailing components and functions such as guard intervals, cyclic prefixes, channel estimation, and link adaption.

Section 4: Advantages and Disadvantages of OFDM
Description 4: Discuss the various advantages of OFDM technology as well as its disadvantages and the challenges it presents.

Section 5: Optical OFDM Transmission Technology
Description 5: Provide an overview of Optical OFDM transmission technology, including the classifications and types of signal synthesis and detection mechanisms.

Section 6: O-OFDM Signal Synthesis Types
Description 6: Explain the different signal synthesis types for optical OFDM, such as FFT-based approaches and optical approaches, and discuss their implementations.

Section 7: O-OFDM Signal Detection Types
Description 7: Describe the types of signal detection for optical OFDM, including direct detection and coherent detection, along with their respective advantages and limitations.

Section 8: MIMO O-OFDM
Description 8: Introduce MIMO in the context of optical OFDM and how it is used to increase the capacity or reduce the transmission impairments.

Section 9: Modulation Formats and Adaptive Modulation
Description 9: Detail the advanced modulation formats and adaptive modulation techniques used in O-OFDM systems to support high-speed transmission.

Section 10: Elastic Optical Network Concept
Description 10: Introduce the concept of elastic optical networks and explain various proposed architectures such as SLICE, FWDM, and Data-Rate Elastic Optical Network.

Section 11: OFDM-Based Elastic Optical Network Architecture
Description 11: Discuss the architecture and components of OFDM-based elastic optical networks, and explain the benefits and requirements for such networks.

Section 12: Data-Rate/Bandwidth-Variable Transponder
Description 12: Describe the data-rate/bandwidth-variable transponder and mechanisms to support multiple data rates using OFDM technology.

Section 13: Bandwidth-Variable Optical Switching
Description 13: Explain the design and functionality of bandwidth-variable optical switching nodes in elastic optical networks.

Section 14: Network-Level Technologies
Description 14: Cover the network-level technologies required for elastic optical networks, including spectrum slot specifications, RSA algorithms, traffic grooming, survivability strategies, and network control and management schemes.

Section 15: Conclusion
Description 15: Summarize the key points covered in the survey and outline the potential future research directions for OFDM-based elastic optical networks.