On Optically Pre-amplified FSO-MISO Non-identical Links with Correlation: Experiment and Analysis

Abstract

In this paper, various link characteristics and bit error rate (BER) performance of a free-space optical (FSO) multiple-input-single-output (MISO) system with repetition cod- ing (RC) is investigated both experimentally and theoretically. The study is performed in the presence of atmospheric turbulence (AT) over a correlated channel with an erbium-doped fiber am- plifier employed at the receiver (Rx). It is shown experimentally that the measured AT levels of two parallel links are different and the links experience non-identical fading influence. The analytical BER expression for an optically pre-amplified correlated FSO- MISO system with non-identical AT channel is derived. The BER results of the considered system with pre-amplifier is compared with the BER results of an FSO system without pre-amplifier, and it is shown analytically that a 2×1 FSO system with pre-amplifier offers better BER performance in terms of coding gain of 6 dB over the system without pre-amplifier. Moreover, it is also shown that the FSO system with RC gives better performance with identical links as compared to non-identical links. Further, it is also revealed that the diversity order of the considered system is independent of correlation and use of pre-amplifier. All the analytical results are validated by comparing them with Matlab simulations.