In situ design method for multichannel gain of a distributed Raman amplifier with multiwave OTDR

We demonstrate a novel approach for the measurement of pump/signal waves interaction in the Raman amplifier (RA), with the use of multiwave optical time-domain reflectometry. With the application of obtained pump-evolution profiles to algorithms based on effective length recalibration, the multichannel Raman gain can easily be predicted with excellent accuracy for the undepleted, distributed RA. As a further extension of this algorithm, an in situ semi-analytic Raman-gain design method is also demonstrated.