Enhancing Performance of Coherent Optical OFDM FSO Communication Link Using Cascaded EDFA

Coherent communication aims to support high-speed dynamic networks by making their installation easier along with their monitoring and maintenance. In addition, Orthogonal Frequency Division Multiplexing (OFDM) which has shown gradual emergence in radio frequency (RF) domain during the past years, has now encroached into the optical domain. Combination of these two provides vigorous dispersion transmission as well as enhanced spectral efficiency. Free Space Optical (FSO) communication link performance deteriorates with scintillations, atmospheric turbulences and weather induced attenuations. The optical amplifiers, their arrangement used in the FSO link design has a drastic influence on the performance of the link. This work involves evaluating the proposed Coherent Optical OFDM FSO communication link at 30 Gbps data rate using Cascaded Erbium Doped Fiber Amplifier. The system has been evaluated in clear weather, rainfall and fog (Moderate to Dense) in terms of Q-Factor, BER, SNR and constellation diagram. The system has been designed considering moderate turbulent environment and geometric losses. The FSO communication link shows optimal performance up to 26 km for clear weather, 3.73 km under rainfall, 1.44 km under moderate foggy and 0.66 km under dense foggy environment.

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