Evaluation of Raman gain coefficient distribution independent of imperfection contributions

We have previously reported a technique for measuring the distribution of the Raman gain characteristics in optical fibers. It is well known that Raman gain characteristics are affected by dopants and the effective areas in optical fibers. The Raman gain coefficient independent of the influence of effective areas will be used to investigate the longitudinal uniformity in fibers. This letter describes a method for evaluating the Raman gain coefficient distribution in a way that distinguishes it from the effects of waveguide imperfections by employing our previously reported technique. Using this method, we performed experiments on various types of fiber, and confirmed that the Raman gain coefficient can be accurately measured.