Performance of All-Optical Amplify-and-Forward WDM/FSO Relaying Systems over Atmospheric Dispersive Turbulence Channels

Abstract

This paper newly proposes and theoretically analyzes the performance of multi-hop free-space optical (FSO) systems employing optical amplify-and-forward (OAF) relaying technique and wavelength division multiplexing (WDM). The proposed system can provide a low cost, low latency, high flexibility, and large bandwidth access network for multiple users in areas where installation of optical fiber is unfavorable. In WDM/FSO systems, WDM channels suffer from the interchannel crosstalk while FSO channels can be severely affected by the atmospheric turbulence. These impairments together with the accumulation of background and amplifying noises over multiple relays significantly degrade the overall system performance. To deal with this problem, the use of the M-ary pulse position modulation (M-PPM) together with the OAF relaying technique is advocated as a powerful remedy to mitigate the effects of atmospheric turbulence. For the performance analysis, we use a realistic model of Gaussian pulse propagation to investigate major atmospheric effects, including signal turbulence and pulse broadening. We qualitatively discuss the impact of various system parameters, including the required average transmitted powers per information bit corresponding to specific values of bit error rate (BER), transmission distance, number of relays, and turbulence strength. Our numerical results are also thoroughly validated by Monte-Carlo (M-C) simulations.

Performance Enhancement of DWDM-FSO Optical Fiber Communication Systems Based on Hybrid Modulation Techniques under Atmospheric Turbulence Channel

“…Furthermore, the DPPM-PAPM pulse and ICC pulse strength are P tr , P XT , respectively for the hybrid modulation techniques over the FSO link. R = η/hv i ,η is the PD quantum efficiency, v i , ν and are the optical frequencies of ICC wavelengths and signal respectively and h is Planck's constant, q is the electron charge, [5,[8][9][10][29][30][31][32][33][34], N o = 0.5(NF × G − 1) hv is the OA power spectral density (PSD) at the single polarization ASEN. NF and G are the noise figure and OA gain G respectively, L = B o m t t s encompass the system modes for the spatial and temporal method [2,8,9,[35][36][37][38][39][40][41][42], B o is the bandwidth of the optical noise for the demux channel and m t is the number of ASEN states.…”

“…Differences in the air and variation between the refractive index structure (RIS) C 2 n and Earth's surface temperature are responsible for the scintillation effects [8]. These findings are focused on the probability density function (pdf) of the Gamma-Gamma (GG) model [5,8,9,[29][30][31][32][33][34].…”