DCF-based fiber Raman amplifiers with fiber grating reflectors for tailoring accumulated-dispersion spectra

The fiber Raman amplifier (FRA) using dispersion-compensation fiber (DCF) as the Raman fiber is studied. Fiber grating reflectors (FGRs) embedded in the amplifier are used to control the travel lengths of the WDM signal channels in the amplifier so that the accumulated-dispersion spectra of the signals in the amplifier can be tailored. The amplifier compensating for the accumulated dispersions of 86 ITU 100 GHz-spaced WDM signal channels in 100 km TrueWave-RS fiber and providing 20 dB gain for each channel is taken as an example, in which the positions of FGRs in the DCF ranges from 2.18 km to 2.68 km. It is shown that its pump power can be utilized more efficiently than the conventional FRA without FGRs. The FGRs can be written on the DCF or inserted into the DCF by splicing. For the latter case, the pump power and noise figure are respectively increased by about 86.6 mW and 0.2 dB per 0.01 dB loss increment of a splice point.