— Free space optical (FSO) communication has become a viable technology for broadband wireless application which offers the potential of high bandwidth capacity over unlicensed optical wavelength. Atmospheric turbulence has most significant impact on the quality of laser beam propagating through the atmosphere over long distance. For optical wireless communication system, most frequently used system is dense wave division multiplexing (DWDM). We are applying 150m channel spacing with 40 GHz bandwidth and 1550nm laser source. FSO channel work like Afocal scheme, it can reduce the size of laser beam, and expected longer free-space transmission in FSO communication, receiver side equal gain combining technique in presence of strong atmospheric turbulence. The signal to noise ratio (SNR), good bit-error rate (BER) performance and clear eye diagram are obtained and will be evaluated numerically for different system parameters. Such as DWDM FSO communication in provided the long transmission distance and high transmission rate, it useful for high speed light based Wi-Fi and Li-Fi applications