makes possible relatively long distance transmission via a multi amplifier cascade the inventors recently measured gain and transmission system bit error rate performance for a broadband 4 channels from 1510 nm to 1570 nm hybrid amplifier based on a single soa and a single raman pump laser that amplifier 100 which has been previously demonstrated for dwdm systems is shown schematically in fig1 a backward propagating semiconductor raman pump laser 120 is coupled to the transmission fiber 110 with a wavelength division multiplexing wdm coupler 130 followed by a conventional polarization independent soa 140 and an optical isolator 150 the raman pump wavelength is chosen to compliment the soa such that the combined gain of the hybrid amplifier is both increased and flattened as compared to the soa alone a plot 200 of measured gains of the components of the hybrid amplifier of fig1 is presented in fig2 specifically that figure shows the measured gain spectra 230 of the soa alone triangles raman amplifier 220 alone diamonds and the hybrid amplifier 250 squares in this case the raman pump laser operated at 1480 nm wavelength with 300 mw coupled into the transmission fiber and the soa gain peak was approximately 1510 nm wavelength the transmission fiber which is necessary to provide raman gain was 60 km of standard reduced water peak fiber ofs allwave u00ae fiber similar performance is expected for other common transmission fiber types including.