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 analyzes and enhances the performance of moment generating function techniques, notably the Chernoff bound (CB) and modified Chernoff bound (MCB), is used to improve the bit-error-rate (BER) performance of an optically pre-amplified for the wavelength division multiplexing (WDM) based on the passive optical network (PON) free-space optical (FSO) communications in the presence of both atmospheric turbulence (AT), amplified spontaneous emission (ASE) noise, and interchannel crosstalk. In the absence of AT and ASE at a data rate of 2.5 Gbps on the 1550 nm wavelength, digital pulse-position modulation (DPPM) systems with coding level (M) of 2 provide about 2.9 dB improvement in average power over at a BER of (depending on the turbulence level) compared with an equivalent on-off keying (OOK) non-return-to-zero (NRZ) in the WDM-PON/FSO system while maintaining minimum bandwidth expansion to leverage the extended reach and enhanced user capacity and considered as a good solution to the bandwidth requirement for future access networks, with potential for higher data rate, improved data security. The receiver sensitivities of M-ary DPPM about 51.4 dBm (~21.9 photons/bit) (CB), and 51.5 dBm (21.4 photons/bit, MCB) can be achieved, which implies an improvement when compared with an OOK-NRZ system (~38 photons/bit) in the non-turbulent atmospheric condition. M-ary DPPM retains its sensitivity improvement over OOK even in the existence of crosstalk while predicting a lower power penalty of about 0.2–3.0 dB for weak turbulence at low coding level (M) 2 in WDM systems.