We successfully demonstrate 40 GB/s 8 channels' Dense Wavelength Division Multiplexing (DWDM) over free space optical (FSO) communication system. Each channel is transmitting 5 GB/s data rate in downstream separated by 0.8 nm (100 GHz) channel spacing with 1.8 GHz filter bandwidth. DWDM over FSO communication system is very effective in providing high data rate transmission with very low bit error rate (BER). The maximum reach of designed system is 4000 m without any compensation scheme. The simulation work reports minimum BER for Return-to-Zero (RZ) modulation format at different channels 1, 4, and 8 are found to be 2.32 −17 , 1.70 −16 , and 9.51 −15 at 4000 m distance, respectively. Sharp increase in BER occurs if data rate and distance increase up to 10 GB/s and 5000 m.

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In this paper, Decision Feedback Equalization (DFE) and Feed forward Equalization (FFE)based on minimum mean square error optimization has been employed to improve the performance of 32 channels, gigabit capacity WDM-PON network. An optical line terminal (OLT) installed at the transmitter end which continuous transmit 32 channels having different colors (wavelengths) of 20GB/s data rate , which is multiplexed by optical multiplexer and transmit through standard single mode fiber (SMF) having length 40km. A link design for 1:64 optical splitters is used as Passive Optical Network (PON) element which creates communication between OLT to different end users. It is observed that FFE and DFE significantly reduce BER by 1.0798e -010 , 1.1556e -011 , 1.2960e -010 and 8.8979e -009 at four different wavelengths 1550nm, 1559.6nm, 1562.8nm and 1574.8nm by using NRZ (non return zero) modulation format at 20GB/s for 64 users having 40km fiber length respectively. Sharp increase in BER 2.6916e -002 , 4.6519e -002 , 3.8804e -001 and 5.1570e -002 occurs if data rate increases up to 25 GB/s.

This paper is successfully demonstrated simulative comparison and investigation of 32 channels with 0.8 nm frequency spacing bidirectional wavelength division multiplexing passive optical network (WDM-PON) having 640 and 320 GB/s data rate in downstream and upstream transmission by using CRZ-DPSK/NRZ modulation formats respectively. The maximum reach of the system has been configured to 100 km by employing different post-dispersion compensation techniques such as EDC, DCF, OPC, and FBG in uplink and downlink transmission for compensate the effect of chromatic dispersion in propagating channel. An EDFA optical amplifier is placed after DCF for boosting the amplitude of weak signals downstream. Apart from this, the RSOA amplifier is installed at the ONT end for reflecting and re-modulates the same wavelengths to the CO terminal without using any external optical light source. The performance comparison of distinct compensation schemes are evaluated in terms of BER, Q factor, and Eye diagrams. It has been observed that the FBG and DCF are more robust compensation techniques as compared to EDC and OPC in the bidirectional WDM-PON. The maximum satisfying value of BER has been observed in downlink and uplink transmissions are 10−26 and 10−13 for FBG and DCF respectively.