Performance analysis of a symbol slicing majority vote combining receiver for binary optical heterodyne ASK with phase-noise-optimised decision thresholds

The performance of a binary optical heterodyne ASK receiver in the presence of photodetector shot noise and laser phase noise has been investigated. To reduce the effects of phase noise on the receiver error rate, the maximum likelihood approach is used to optimise the decision threshold on the basis of the severity of phase noise indicated by the laser linewidth. It is assumed that the receiver uses symbol slicing and majority vote decision combining. Threshold optimisation is applied to each slice (chip) of the received bit duration. It is found that the receiver performance can be significantly improved by threshold optimisation. Majority voting is also found to improve the receiver performance for a wide range of signal-to-noise ratio values.