Factors Affecting Coherent-Detection Sensitivity

Coherent detection plays an important role in coherent optical communication. Highly sensitive coherent-detection systems can significantly increase the distance of coherent optical communication. Targeted corrections can be made to improve the detection sensitivity by studying the factors that affect it. The principle of coherent detection is to coherently mix the signal light and local-oscillator light and then recover the signal, according to the information carried by the mixed signal. This chapter analyzes the influence of thermal noise, shot noise, wavefront distortion, polarization misalignment, beam-spot size deviation, optical-axis deflection, coupling efficiency, detector performance, preoptical amplifiers, and other factors on the sensitivity of coherent detection. We summarize the research results of domestic and foreign scholars in this field in recent years and, finally, provide prospects for its future development direction.