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

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 83.32 km 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 × 120 Gb/s DP-QPSK coherent wavelength division multiplexing transmission system are presented. We report ~10 dB RIN reduction and 0.7 dB Q factor improvement, which allows a 1250 km transmission distance increase compared with conventional low RIN and narrowband first-order pump sources. We also demonstrate that, bidirectional pumping with only broadband first-order forward pumping at 50 mW shows the lowest RIN transfer from pump to signal. This extends the transmission reach up to 8332 km with maximum distances increased by 1250 and 1667 km compared with conventional backward only and first-order semiconductor forward pumped bidirectional pumping, respectively.