Pump-wavelength dependence of Raman gain in single-mode optical fibers

The magnitude of the stimulated Raman gain spectrum depends 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 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.