 It will also serve to outline the evolution of such systems over the last 10 or so years.As stated above, wavelength-converting transponders served originally to translate the transmit wavelength of a client-layer signal into one of the DWDM system's internal wavelengths in the 1,550 nm band (note that even external wavelengths in the 1,550 nm will most likely need to be translated, as they will almost certainly not have the required frequency stability tolerances nor will it have the optical power necessary for the system's EDFA).In the mid-1990s, however, wavelength converting transponders rapidly took on the additional function of signal regeneration.