Performance evaluation and enhancement of the modified OOK based IM/DD techniques for hybrid fiber/FSO communication over WDM-PON systems

In this paper, we have studied the performance evaluation and enhancement of a wavelength-division-multiplexing (WDM) for the passive optical network (PON) in the hybrid fiber/free-space optical (HFFSO) communication system using the modified on-off keying (OOK) based intensity modulation and direct detection (IM/DD) techniques. This work describes the design and analysis of the 8-channels WDM based on the PON-HFFSO transmission system at 2.5 Gbps under different atmospheric turbulence (AT) conditions. Inter-channel crosstalk (ICC), fluctuation, amplified spontaneous emission noise, AT, and impairments are investigated in the paper. A hybrid fiber/WDM-FSO over the PON structure using IM/DD and OOK significantly improves reliability link and accessibility as well as data rate, also improves the system capacity; hence the proposed model will reduce power consumption while maintaining system efficiency. Both impairments and ICC are investigated here and the results are presented in the form of bit-error-rate (BER), transmission distances, the required optical power, and electrical signal-to-noise ratios (SNRs). The system uses the modified OOK based on IM/DD to implement adaptive and electrical SNRs detection thresholds. Numerical results show that the SNR gap between the electrical-SNR-optimized detection system and adaptive detection system is 2.2 dB and 4.2 dB at a BER of 10(-5)without a state offset xi = 0 and xi = 0.21, respectively. The proposed model enhances performance in terms of BER and electrical SNRs. An improvement in the power penalty of 2.0-4.0 dB at a BER of 10(-12)can be potentially achieved using the modified OOK technique when impaired by the weak turbulence.