Spectrum sliced wavelength division multiplexing based free space optical communication employing differential quadrature phase shift keying and optical frequency comb generation

A spectrum-sliced (SS) Wavelength division multiplexing (WDM) based Free-space optical (FSO) communication system at a data rate of 5x32 Gbps is proposed in this research article. Based on the concept of Optical Frequency Comb Generator (OFCG), the optical spectrum is sliced into 32 parts so that the data rate is improved by 32 times. A cost-efficient, 160 Gbps WDM FSO system is designed and implemented using the Opti-system software. In WDM, multiple lasers are needed. Hence, the price of the system increases. To reduce cost, an optical multicarrier generation system is required. The proposed system design generates multiple wavelengths, thereby splitting the available spectrum into 32 channels with a fixed channel spacing of 25 GHz. The produced optical comb has a width of 10 nm, starting from a wavelength of 1544.8 nm to 1555.2 nm. The proposed work reveals that the differential quadrature phase shift keying (DQPSK) based SS-WDM FSO system has higher performance compared to intensity modulation formats and other differential phase modulation formats. Considering various values of FSO link distances, antenna diameters of transmitter and receiver, beam divergence and, thus determining the values of performance metrics such as Q-factor and bit error rate (BER), the DQPSK-based SS-WDM FSO system is simulated.