Optimization of Raman amplifier using Raman frequency modeling for arbitrary GeO/sub 2/ concentration in silica fiber

As the wavelength division multiplexing (WDM) technique is established as a standard for optical communication system upgrade, Raman amplifiers based on silica fibers has been intensively studied for their flexible gainband control and potential as an alternative to rare earth doped fiber amplifiers. Raman amplifiers showed large gain (/spl sim/30 dB) at the 1st Stokes shift with the pump power of 300 mW and wide bandwidth over 90 nm by using cascaded pumps of different wavelengths. Recently low loss and high Ge doped silica fiber has been developed to reduce the pumping power. The evolution of 1st and 2nd Stokes shift, however, has not been rigorously analyzed including the effects of GeO/sub 2/ both on the gain and Rayleigh scattering loss. In the study, we obtained the amplified gain and optimum length of Raman medium for various germanium concentrations using Raman frequency modeling whose governing equations are given.