Abstract

With the prevalence of fibre Raman amplifiers (FRAs) in modern optical communications systems, accurate and detailed analysis tools become essential for obtaining results on system performance. Models for FRAs based on both analytical [1] and numerical [2] analyses have been reported previously. Analytical solutions to the rate equations (1-5) can be readily obtained if the pump depletion terms are omitted. This has reasonable accuracy with low signal and pump powers but becomes increasingly inaccurate when considering the powers used in modem systems. Although [1] considers the effects of pump depletion, both higher order Stokes wave generation and amplified spontaneous scattering (ASS) noise are neglected. Similarly, the model in [2] is valid only with small signal power levels, where the amplifier is operated in the undepleted pump regime. In this paper we present, for the first time to the authors knowledge, a full numerical analysis of the performance of co- and counter- propagating FRAs including terms for both pump depletion, higher order Stokes wave generation (up to third order) and ASS noise simultaneously. We demonstrate that, with the powers available in modem Raman pump lasers and with realistic signal powers, the omission of the pump depletion and higher order Stokes wave generation can lead to significant errors in performance evaluation. Equations (1-5) represent the differential equations that govern the signal and pump propagation in a co-propagating configuration, these have been modified to include the higher order Stokes wave generation, ASS noise and pump depletion terms.

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