Dagang Jiang

Principle and performance analysis of coherent tracking sensor based on local oscillator beam nutation.

By integrating coherent tracking sensor functionality into a coherent communication receiver, a dual-function receiver with coherent boresight error sensing is developed for tracking in coherent free-space optical communication systems. The sensor principles are analyzed according to optical interference theory, and the boresight error detection algorithm and small signal linear model are derived. Analysis of local-oscillator beam nutation on system performance shows that the best nutation half-angle is 0.5-1 μrad, the noise equivalent angle is less than 0.02 μrad, and the communication sensitivity degradation is 0.2-0.6 dB. This technology opens new avenues for free-space optical communication system design.

Optimal optical communication terminal structure for maximizing the link budget

Ordinary inter-satellite optical includes at least three optical paths for acquisition, tracking and communication, the three optical paths work simultaneously and share the received power. An optimal structure of inter-satellite optical communication terminal with single working optical path at each of working stages of acquisition and communication is introduced. A space optical switch based on frustrated total internal reflection effect is applied to switch the received laser power between the acquisition sensor and the communication sensor between the stages of acquisition and communication, this is named as power fusion which means power is transferred for shutting down unused optical path. For the stages of tracking and communication, a multiple cells sensor is used to accomplish the operation of tracking while communication, this is named as function fusion which means accomplishing multiple functions by one device to reduce the redundant optical paths. For optical communication terminal with single working path structure, the total received laser power would be detected by one sensor for each different stages of acquisition, tracking and communication, the link budget would be maximized, and this design would help to enlarge the system tolerance and reduce the acquisition time.

Dynamic link attenuation of inter-satellites homodyne BPSK optical communication

This paper summarizes the results of a dynamic link attenuation probability study in inter-satellites homodyne BPSK optical communication system. The impacts of the pointing and tracking error on the coherence receiving power are investigated analytically. To evaluate the requirement of optical system aberrations, the link attenuation caused by the aberrations is analyzed. By means of numerical simulation, the probability density function and the cumulative distribution function of bit error probability are calculated by the frequency histogram method.

A novel technology combined with free space optics communication and laser ranging

A solution is proposed, which combined with FSO communication and laser ranging in order to effectively integrate two payloads. It is a transformation of feedback pulsed laser ranging. Laser ranging hardware and FSO communication hardware share a lot in common. Detailed description of working principle, error analysis and elementary experiment result is also included. The further analysis indicates that the measurement precision can reach sub-millimeter by counting more ranging period. Moreover, when temperature varies 30°C, the measure distance varies 2.25cm. In this case, temperature control is necessary for sub-millimeter measurement.