the abstract of the paper goes like this
We successfully demonstrate 40 GB/s 8 channels’ DenseWavelength DivisionMultiplexing (DWDM) over free space optical (FSO)
communication system. Each channel is transmitting 5 GB/s data rate in downstream separated by 0.8nm (100GHz) channel
spacing with 1.8GHz 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 4000m 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