Design and analysis of multiplexed FSO system with DPSK and Manchester coding

In spite of several advantages of free space optics (FSO) such as huge bandwidth, license-free communication and high electromagnetic interference, immunity over radio-frequency technology, these systems are also severely affected by fog and atmospheric turbulence. Generally, the performance of such communication systems can be measured by the two important parameters such as bit error rate (BER) and Q-factor. To improve the average BER performance of the system various advanced modulation techniques with different coding schemes have been proposed in the past literature. Thus in the proposed system, Manchester coding technique is used with the differential phase shift keying (DPSK) modulated signal. The designed system is compared with the differential phase shift keying with the 2-array pulse position modulation (DPSK-2PPM) scheme and the conventional DPSK system. Manchester encoding synchronizes the signal itself; hence, it minimizes the error rate and optimizes the reliability of the proposed system. In addition, a 16-channel wavelength division multiplexing (WDM) FSO system is considered for improving the spectral efficiency of the system. For analyzing, the low to high turbulence level of atmosphere, Gamma-Gamma type channel model is preferred.