Pump-to-signal FWM of co-pumped Raman amplifier for remote pumps supervisory

We propose a novel remote Raman pumps monitoring technique based on the pump-to-signal four-wave-mixing (FWM) in a 50-m long highly nonlinear dispersion-shifted photonic crystal fiber. The health information of the pumps can be reproduced to the new FWM signal accompanying the transmission signal through the pump-to-signal FWM. As a result, the modulation frequency limitation for cross gain modulation can be avoided effectively, and no degradation of the transmission system is induced by this technique.