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

Abstract

In this paper, we enhance the performance efficiency of the free-space optical (FSO) communication link using the hybrid on-off keying (OOK) modulation, M-ary digital pulse position modulation (M-ary DPPM), and M-pulse amplitude and position modulation (M-PAPM). This work analyzes and enhances the bit error rate (BER) performance of the moment generating function, modified Chernoff bound, and Gaussian approximation techniques. In the existence of both an amplified spontaneous emission (ASE) noise, atmospheric turbulence (AT) channels, and interchannel crosstalk (ICC), we propose a system model of the passive optical network (PON) wavelength division multiplexing (WDM) technique for a dense WDM (DWDM) based on the hybrid fiber FSO (HFFSO) link. We use eight wavelength channels that have been transmitted at a data rate of 2.5 Gbps over a turbulent HFFSO-DWDM system and PON-FSO optical fiber start from 1550 nm channel spacing in the C-band of 100 GHz. The results demonstrate (2.5 Gbps × 8 channels) 20 Gbit/s-4000 m transmission with favorable performance. In this design, M-ary DPPM-M-PAPM modulation is used to provide extra information bits to increase performance. We also propose to incorporate adaptive optics to mitigate the AT effect and improve the modulation efficiency. We investigate the impact of the turbulence effect on the proposed system performance based on OOK-M ary- PAPM-DPPM modulation as a function of M-ary DPPM-PAPM and other atmospheric parameters. The proposed M-ary hybrid DPPM-M-PAPM solution increases the receiver sensitivity compared to OOK, improves the reliability and achieves a lower power penalty of 0.2–3.0 dB at low coding level (M) 2 in the WDM-FSO systems for the weak turbulence. The OOK/M-ary hybrid DPPM-M-PAPM provides an optical signal-to-noise ratio of about 4–8 dB of the DWDM-HFFSO link for the strong turbulence at a target BER of 10−12. The numerical results indicate that the proposed design can be enhanced with the hybrid OOK/M-DPPM and M-PAPM for DWDM-HFFSO systems. The calculation results show that PAPM-DPPM has increased about 10–11 dB at BER of 10−12 more than the OOK-NRZ approach. The simulation results show that the proposed hybrid optical modulation technique can be used in the DWDM-FSO hybrid links for optical-wireless and fiber-optic communication systems, significantly increasing their efficiency. Finally, the use of the hybrid OOK/M-ary DPPM-M-PAPM modulation schemes is a new technique to reduce the AT, ICC, ASE noise for the DWDM-FSO optical fiber communication systems.

MGF Methods for Fixed and Gain Saturated Optically Preamplified FSO Links Impaired by Misalignments and Atmospheric Turbulence

“…Average Transmitted Power (dBm) , the SPA performed better than the GA and the MCB; with the MCB recording the least performance. Note that these results do not invalidate the use of the MCB in FSO communication systems because the MCB, which has been known to give comparable and upper bounds on the GA with low and high gain preamplifiers respectively [12], [15], has been proposed as a preferred performance evaluation method [7], [12]. Also, systems WoPE ( r W z = 5) performed ) and WPE (…”

Performance enhancement of UAV relay-assisted free-space optics systems with pointing errors

“…where ℎ 𝑡 is the atmospheric channel's attenuation and AT coefficient; ℎ 𝑎 represents the link interrupt coefficient, which denotes whether the spot is detected on the detection plane; and ℎ 𝑔 is the geometric and PE deviation coefficient, which denotes the position deviation between the spot center and the lens center at the receiving end. The Gamma-Gamma (GG) model can be used to characterize the distribution of ℎ 𝑡 in terms of the attenuation of the optical signal caused by air turbulence [9][10][11][12], [22][23][24][25][26]:…”

“…where Г(•) is Gamma function, 𝑘 𝑛 (•) is the n th order modified second kind of Bessel function, 𝛼 and 𝛽 indicate the effective numbers of the large-scale and small-scale eddies, respectively [9][10][11][12], [22][23][24][25][26]:…”

“…where k is the wave number, C n 2 is the atmospheric refractive index structural (ARIS) parameter [9][10][11][12], [22][23][24][25][26], and L is the FSO distance [9][10][11][12], [22][23][24][25][26]. The Gamma-Gamma model's atmospheric turbulence is simulated in this work using the phase screen approach [22][23][24][25][26][27][28][29].…”

Performance enhancement of UAV-FSO communication links with pointing errors

“…where the Rytov variance is expressed as: σ R 2 =1.23k 7 6 C n 2 L 11 6 (6) where k is the wave number, C n 2 is the atmospheric refractive index structural (ARIS) parameter [9][10][11][12], [22][23][24][25][26], and L is the FSO distance [9][10][11][12], [22][23][24][25][26]. The Gamma-Gamma model's atmospheric turbulence is simulated in this work using the phase screen approach [22][23][24][25][26][27][28][29].…”