الفهرس 
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Abstract
In this thesis, performance enhancement of a free space optical (FSO) communication system using the hybrid modulation techniques for the M-ary digital pulse position modulation (M-ary DPPM), on-off keying (OOK) modulation, and M-pulse amplitude and position modulation (M-PAPM) is achieved. This thesis analyzes and enhances the performance of the Chernoff bound, modified Chernoff bound, and moment-generating function techniques, to improve the bit error rate (BER) performance. A system model of the wavelength division multiplexing (WDM) based on the passive optical network (PON) for the hybrid fiber FSO (HFFSO) link in the presence of both atmospheric turbulence (AT), amplified spontaneous emission (ASE) noise, and inter-channel crosstalk (ICC) is proposed. The M-ary DPPM-M-PAPM modulation to deliver extra information bits to achieve higher efficiency is proposed. Also, propose to add adaptive optics to combat the ICC interferences to reduce the AT effect and enhance reliability performances. The proposed approach of the M-ary DPPM-M-PAPM improves the receiver sensitivity over OOK and enhances the performance efficiency and achieves a lower power penalty of 0.2–3.0 dB for weak turbulence at low coding level (M) 2 in the WDM-FSO systems. At a target BER of 〖”10” 〗^(-”12” ), the hybrid OOK/M-ary DPPM-M-PAPM offers about 4-8 dB optical signal to noise ratio improvements over the hybrid modulation techniques of the M-DPPM-M-PAPM of the ST for the WDM- HFFSO link. Simulation results show that the proposed design can enhance the efficiency and BER performance using the hybrid OOK/M-DPPM and M-PAPM for WDM-HFFSO systems. Finally, to solve the problem of impairments and ICC and ASE, the use of the hybrid OOK/M-ary DPPM-M-PAPM modulation schemes is a new approach for power-efficient and powerful treatment to reduce the effects of the AT, ASE noise, and ICC.Keywords: amplified spontaneous emission (ASE) noise; interchannel crosstalk; WDM/PON system; hybrid modulation techniques; free space optical communications; hybrid OOK/M-ary DPPM-M-PAPM; hybrid fiber FSO (HFFSO) link; modified Chernoff bound.