Exact determination of scaling of the Raman gain efficiency in silica fibers

This paper presents a theoretical and experimental study on the behavior of the Raman gain efficiency for any Stokes and excitation wavelength. Analyzing the Raman threshold for two adjacent Stokes we find a mathematical relationship to the Raman gain efficiency. This equation scales inversely with wavelength and directly with the fiber attenuation, and also provides approximate quantities to numbers already published. From experimental data for a LEAF fiber, we construct two curves, one based on our equation and the other based on the approach normally used, and the comparison of the two curves reveals significant errors. Additionally, we show that the spectrum of the Raman gain efficiency has the same shape as the attenuation spectrum. (paper)