Performance Analysis of Hermite Gaussian 8×40 Gb/s DWDM-FSO System using Advance Modulation Schemes

Abstract

Abstract Transmission of high-speed optical signals across the free space channel is highly dependent on external characteristics such as scintillation and attenuation as a result of atmospheric conditions that are constantly changing. This paper describes the architecture of an 8×40 Gbps dense wavelength division multiplexed (DWDM)-FSO transmission system based on Hermite Gaussian (HG) channels and incorporates various advanced modulation techniques. In addition, the implementation of a spatial mode laser and an optical boost amplifier decreases the effect of degradation caused by atmospheric attenuation and extends the optical link distance. The performance of the proposed system design is investigated for six modulation schemes including 64-QAM, 16-QAM, 4-QAM, 8-PSK, DPSK, and DQPSK modulations in different atmospheric attenuations conditions under a strong Gamma-Gamma (GG) turbulent channel. It is reported that the optical link performance degrades exponentially with an increase in signal to noise ratio (SNR) for the modulation schemes listed above. 4-QAM and DPSK modulations outperform the rest of the modulation methods for low SNR values as the optical link distance increases. The successful signal transmission of 8×40 Gb/s data over the transmission link distance of about 5 km with an acceptable BER level of 10− 6 is achieved.