Abstract
An analytical model is developed for a non-Hermitian coherent-optical OFDM FSO system with space frequency block code (SFBC) and polarization diversity. Analysis is carried out for a non-Hermitian OFDM FSO link with SFBC coding to evaluate the effect of cross polarization induced crosstalk in presence of channel impairments such as atmospheric turbulence. Expressions are developed for signal to noise plus crosstalk ratio for a given amount of polarization misalignment angle. Considering the probability density function of the misalignment angle to be Maxwellian distributed and Gamma–Gamma distribution for strong atmospheric turbulence, the average bit error rate (BER) is determined. Results are evaluated without and with strong atmospheric turbulence. Computed result show that there is significant improvement on receiver sensitivity due to polarization diversity and coding gain due to SFBC. Further, system suffers power penalty due to crosstalk due to cross polarization and as well as turbulence. Results show that, there is 38 dB improvement in receiver sensitivity due to polarization diversity without SFBC in presence of strong turbulence at a BER of 10−12 considering local oscillator power is 5 mW and link distance is 2000 m. At a given BER of 10−12, penalty due to crosstalk is found to be 3.3 dB for mean misalignment angle of 40 when link distance is 2000 m. Finally, it is noticed that, the amount of coding gain due to SFBC is found to be 7.5 dB at a BER of 10−12.
Published Version
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