Performance analysis of optical receivers with space diversity reception

The performance of digital and analogue direct-detection optical receivers with space diversity reception is analysed. The cumulative probability distribution of the received signal is calculated for M-branch diversity and equal-gain combining receivers. For a given probability of detection, the permissible threshold detection level is shown to increase with the number of diversity branches. The improvement in carrier-to-noise ratio (CNR) is shown to be higher for selection diversity compared to combining diversity detection. Optimum diversity array spacing is calculated; this shows the practicality of space diversity systems.