Pump-Wavelength Dependence of Raman Gain in Single-Mode Optical Fibers
Nathan R. Newbury
The magnitude of the stimulated Raman gain spectrum will depend on the absolute wavelength of the pump laser. For many fibers, this dependence can be cast as a simple scaling of the overall gain curve according to a power-law dependence on the pump wavelength. We present three methods of measuring this scaling: estimation from Raman gain theory and known fiber parameters, a brute-force comparison of gain versus pump wavelength, and finally a more elegant comparison of the asymmetry in the Stokes and anti-Stokes Raman gain spectrum at a fixed pump wavelength. We discuss the advantages of the asymmetry technique, which yields the full wavelength dependence of the Raman gain with low uncertainty using only a single pump laser, a broadband source, and an optical spectrum analyzer. Finally, we report on the pump-wavelength scaling of the Raman gain for a number of standard transmission fibers.