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

摘要

This paper presents a new detection scheme namelyDouble Carrier Modulation/Differential Detection(DCM/Diff.D) for free space optical (FSO), to provide alonger transmission distance in the presence of severeatmospheric attenuation. Atmospheric attenuation is themain challenge for FSO or also known as WirelessOptical Communications (WOC). In order to tolerate thiseffect either link distance or link availability has to becompromised. This scheme uses amplitude subtractionbetween original data bits and their inversion to provide asimple dynamic decision making scheme. The inverteddata basically serve as the threshold in place of theconventional externally injected voltage. Using thisscheme, we perform a simulation under heavy rainfallcondition of 8.33x10-4 cm/sec in Subang area, Malaysia at2.5 Gb/s and 10 Gb/s with 0 dBm of optical transmitterpower.