Research Of Coherent Homodyne Detection System Based On Sub-carrier Modulation

In order to satisfy with the the requirement of high rate, high sensitivity by space laser communication. This topic has conducted the research the system of homodyne coherent detection based on Sub-Carrier Modulation. The paper mainly focuses on Sub-Carrier Modulation's influence on the performance of the Optical Phase-Locked Loop(OPLL) is analyzed and validated, the design and experiment of the system is also completed. The study of the OPLL is of great importance in the field of space laser communication.This article first introduces the fundamental principles of space laser communication system and the types of coherent detection. Theory models are set up for few typical optical phase-locked loops, and comparison to their performance were made. In order to satisfy the requirements of OPLL frequency tuning which are high rate and wide range, this paper proposes a new structure of OPLL that the Sub-Carried Optical Phase-Locked Loop(SC-OPLL).Detailed introduction of the fundamental principle of Sub-Carrier Modulation technology was made by this paper. So did the analysis of the influence Sub-Carrier Modulation technology has on the performance of OPLL. According to these requirements of performance, we made the homodyne coherent communication system design simulation and experimental test. Experimental results show that when the system at the same modulation rate, bit error rate and other conditions, the use of sub-carrier phase-locked loop can improve the detection sensitivity of homodyne coherent system.