RAYLEIGH-SCATTERING LIMITATIONS IN DISTRIBUTED RAMAN PRE-AMPLIFIERS

The properties and fiber dependence of distributed Raman pre-amplifier s and, in particular, the effects of Rayleigh backscattering, which li mits the sensitivity improvements that can be realized, is discussed, Bit-error-Fate (BER) measurements show improvements in the effective r eceiver sensitivity of 6.2 and 7.0 dB for dispersion shifted fiber (DS F) and silica-core fiber (SCF), respectively. Theoretical predictions of the effective noise figure based on measured fiber parameters indic ate improvements of 6.6 dB for DSF and 7.4 dB for SCF in good agreemen t with the measured optical SNR, The optimum receiver sensitivity is o btained in DSF with less than 600 mW of pump power, whereas the 0.8-dB superior performance of the SCF requires approximately 1 W.