Performance Evaluation and Enhancement of M-Ary DPPM Modulation for WDM-PON/FSO Systems Impaired by Atmospheric Turbulence, Interchannel Crosstalk, and ASE Noise

Abstract This paper analyses and enhances the performance of moment generating function (MGF) techniques, in particular, Chernoff bound (CB) and modified Chernoff bound (MCB). Also, we improve the M-ary digital pulse-position modulation (M-ary DPPM) systems performance of a wavelength division multiplexing (WDM) based on the passive optical network (PON) free-space optical (FSO) communications in the presence of the atmospheric turbulence (AT), amplified spontaneous emission (ASE) noise, and interchannel crosstalk (ICC). This is a technology that can have extended leverage, higher data rates, power-efficient, and is considered an ideal option for the provision of bandwidth for potential access networks. The MCB exceeds the Gaussian approximation at high gain (G = 30) and gives the tightest bound upon the bit-error-rate (BER) compared to the CB at a low gain (G = 8). In the absence of AT and at a data rate of 2.5 Gbps on the 1550 nm wavelength, DPPM scheme with coding level (M) of 2 provide about 2.9 dB improvement in average power over at a BER of \({\text{10}}^{-\text{9}}\)compared with an equivalent on-off keying (OOK) non-return-to-zero (NRZ) in the WDM-PON/FSO system. The sensitivity of M-ary DPPM modulation remains improved over OOK even though the ICC is present. The lower power penalty (PP) is predicted to be approximately 0.2-3.0 dB in WDM-FSO systems for low coding (M) 2. At a target BER of \({\text{10}}^{-\text{12}}\), the hybrid OOK-NRZ/M-ary DPPM offers about 4-8 dB optical signal-to-noise-ratio improvements over M-DPPM of the ST for the WDM-FSO link. Finally, the use of the M-ary DPPM and the optical relaying amplification technique is a powerful treatment for mitigating the impacts of ASE noise, AT, and ICC.