Performance Analysis of OOK-NRZ and OOK-RZ digital Modulation Techniques for Free Space Optical Communication System

Abstract

The performance of modulation techniques is frequently compared in terms of the average received optical power required to achieve a desired bit error rate at a given data rate. The power spectral density of OOK-NRZ and OOK-RZ data signals with pulse duty cycles and modulation formats have significant power contents at DC and low frequencies. Whereas the bandwidth efficiency depends on the duty cycle. Moreover the RZ does not support sample clock recovery at the receiver because it allows a long low signal without any 0 to 1 transition. Therefore, bit stuffing is necessary which further decreases bandwidth efficiency.