Transmission performance of hybrid WDM-FSO system for using diversity multiplexing in the presence of optical nonlinearities and fading

In this paper, we have theoretically analyzed the transmission performance of wavelength division multiplexed (WDM) free-space optical communication (FSO) link in the presence of optical and wireless nonlinearities. In order to mitigate the nonlinearities due to atmospheric turbulence and optical path, spatial multiplexing technique has been utilized in conjunction with advanced modulation formats like CS-RZ, QPSK and, DSPK and QAM has been employed. A complete theoretical model and simulation study has been carried out. Our analysis shows that modulation formats QAM, DPSK and QPSK outperforms CS-RZ in the presence of strong and medium turbulence. The analysis further shows that using spatial multiplexing (MIMO), QAM has 5.1 dB advantage over CS-RZ and 1.6 dB over DPSK and QPSK modulations at FEC threshold 3.8×10
^-3
. The WDM-FSO system can transport wireless signal upto 36 Km at the FEC threshold.