Design And Preliminary Test Of Heterodyne Weak Light Optical Phase Locking

Laser Ranging System is one of the key techniques for the next-generation mission of low-low tracking Earth gravity field recovery and the space borne gravitational waves detection. The optical phase-locked loop(OPLL) is compulsory to inter-satellite transponder laser ranging. In order to improve the precision of the OPLL of intersatellite laser ranging, we developed a heterodyne OPLL and compared its performance with the homodyne OPLL that we had made already.In this thesis, introduce the space borne gravitational waves detection missions and the Earth gravity field measurement missions are introduced first. Focusing on the Chinese low-low tracking gravity field measurement project(SAGM), detailed discussions on the basic principles of the OPLL used in inter-satellite laser ranging system are given. We built an analog-type OPLL system, including voltage-controlled oscillator(i.e., laser), phase detection and loop filter. In order to analyze the feasibility of this heterodyne OPLL, we used Multi Sim to do a preliminary simulation and verified its performance. We made the heterodyne OPLL circuit board, and built up the heterodyne phase-locked experimental setup. We have succeeded in weak-light phase locking for 100 u W(local laser power) and 10 n W(received laser power) laser beams. The in-loop phase residual error can achieve 4 × 10-4rad??Hz @0.1Hz, which satisfies the demand of for the SAGM mission. Long time phase locking and the locking state can be lasted for 10 hours.