An enhanced combining technique of homodyne ASK optical system with laser phase noise

A new method to detect binary optical homodyne amplitude shift keying (ASK) signals in the presence of laser phase noise and receiver shot noise is presented. This method is rely on an efficient least square (LS) algorithm to mitigate the negative effects of phase noise error. The error rate performance of non-ideal ASK system is investigated under LS detection and the signal-to-noise ratio (SNR) gain penalty is observed. To show the effectiveness of the proposed LS combining technique we compared our results for non-ideal systems with some previous results in the literature. The numerical results obtained through this work showed that LS technique has the ability to reduce the SNR gain penalty caused by the lasers phase error, and hence, can be used in any wire-line or wireless coherent systems suffer from imperfect (non-ideal) phase recovery.