On the Mitigation of RIN Transfer and Transmission Performance Improvement in Bidirectional Distributed Raman Amplifiers

Abstract

We develop a novel broadband first order Raman pump for use as a forward pump in transmission experiments. Our results show significant signal relative intensity noise (RIN) reduction, to a level comparable to backward only pumping. The corresponding optical signal to noise ratio can be improved in dual and first order forward pumped 83.32km bidirectional distributed Raman amplifiers by using the proposed broadband pump as a first order pump. A detailed experimental characterization of RIN, signal power evolution and performance of a 10-120Gb/s DP-QPSK coherent WDM transmission system are presented. We report ~10dB RIN reduction and 0.7dB Q factor improvement which allows a 1250km transmission distance increase compared with conventional low RIN and narrowband 1st order pump sources. We also demonstrate that, bidirectional pumping with only broadband 1st order forward pumping at 50mW shows the lowest RIN transfer from pump to signal. This extends the transmission reach up to 8332km with maximum distances increased by 1250km and 1667km compared with conventional backward only and 1st order semiconductor forward pumped bidirectional pumping respectively.