Cross-Gain Modulation Mitigation in Semiconductor Optical Pre- Amplifiers Using a New Synthetic Filter for NRZ-Based WDM Transmission Systems

A new methodology to synthesize an optical filter that mitigates SOA-induced cross-gain modulation in intensity-modulation with direct detection (IM-DD) WDM transmission systems is proposed and its efficacy is numerically demonstrated. The approach relies on calculation or measurement of the propagating optical field at the input and output of the SOA to synthesize a filter transfer function for a particular channel. The filtering action can be applied at the demultiplexing stage. Through the use of BER performance curves, validation of this novel technique is demonstrated in an 8 × 50 Gb/s pre-amplified WDM system for fibre lengths ranging from 0 to 40 km. This research work thus represents an original effort to overcome the effect of nonlinear cross-talk induced by SOA nonlinearities in multi-channel short-reach transmission systems, thus leveraging the application of these active devices in the telecommunications realm.