 Some technologies are capable of 12.5 GHz spacing (sometimes called ultra dense WDM).New amplification options (Raman amplification) enable the extension of the usable wavelengths to the L-band (1565 nm-1625 nm), more or less doubling these numbers.Coarse wavelength division multiplexing (CWDM), in contrast to DWDM, uses increased channel spacing to allow less-sophisticated and thus cheaper transceiver designs.