Performance Enhancement in Optical Costas Loop Through Phase Subtraction

Abstract

The modified Optical Costas loop (OPLL) for coherent optical detection has been presented in this paper. It contains all the components of the standard OPLL and an extra phase modulator. The detail theory and performance analysis have been studied for the proposed loop, considering laser phase noise in presence of loop delay. It has been found from the result obtained that the tracking performance of the proposed loop improves to a great extent and hence the laser linewidth can be considerably relaxed for the purpose of synchronus detection in presence of the additional phase control arrangement.

Indexing terms:

• Optical phase locked loop
• Short noise
• Phase noise
• Loop natural frequency
• Phase error variance
• Loop propagation delay
• Laser linwidth
• Bit error rate