Mitigation of Dispersion and Turbulence in a Hybrid Optical Fibre and Free-Space Optics Link Using Electronic Equalisation

Transmission of a 25 Gbps non-return to zero signal over a hybrid link of 20 km standard single-mode fibre and 500 m free-space optics under weak-to-moderate turbulence regimes is demonstrated via simulation to provide a practical solution for the last-mile access networks. Even though there are several complex mitigating methods to reduce the waveform distortions caused by both the fibre chromatic dispersion and atmospheric turbulence, we provide and discuss a simple approach using an electrical equalizer at the receiver. The simulation results demonstrate that, the proposed equalization technique offer about an order of magnitude improvement in the bit error rate at the received optical power of -20 dB m and a receiver sensitivity gain of 1.5 dB at the 7% forward error correction limit.