DOUBLE CARRIER MODULATION/DIFFERENTIAL DETECTION FOR MULTI-GIGABITS-PER-SECOND, FREE SPACE OPTICAL

摘要

This paper presents a new detection scheme namely Double Carrier Modulation/Differential Detection (DCM/Diff.D) for free space optical (FSO), to provide a longer transmission distance in the presence of severe atmospheric attenuation. Atmospheric attenuation is the main challenge for FSO or also known as Wireless Optical Communications (WOC). In order to tolerate this effect either link distance or link availability has to be compromised. This scheme uses amplitude subtraction between original data bits and their inversion to provide a simple dynamic decision making scheme. The inverted data basically serve as the threshold in place of the conventional externally injected voltage. Using this scheme, we perform a simulation under heavy rainfall condition of 8.33×10{sup}(-4) cm/sec in Subang area, Malaysia at 2.5 Gb/s and 10 Gb/s with 0 dBm of optical transmitter power.