Inter-satellite laser-ranging based on intradyne coherent detection.

With the development of laser communication networking, laser-ranging technology is becoming more and more applicable. In this paper, high-accuracy ranging is implemented based on intradyne coherent detection at a communication rate of 1048.576 Mbps. The ranging accuracy is affected by clock phase calculation error and code loop track error. Parallel clock phase difference calculation, frame head correlation, and ranging ambiguity region handle are combined with the ranging calibration method, realizing millimeter-level corrected distance measurement. Dynamic range measurement above 1 m is proven to be continuous through the ranging ambiguity region handle. In addition, high-precision clock frequency deviation between two asynchronous terminals can be obtained through derivation of one-way distance at static ranging or by derivative of distance difference at bidirectional ranging. The methods proposed in this paper are verified by inter-satellite laser-ranging on orbit, and the results are analyzed.

Experimental verification of coherent tracking system based on fiber nutation.

We report a coherent tracking system based on fiber nutation for inter-satellite beaconless laser communication, which uses a piezo-electric ceramic tube (PCT) to drive the end face of single mode fiber (SMF) for nutation, and uses coherent demodulation method to directly calculate the boresight error from the intensity envelope fluctuation of signal light. The method is given theoretically and verified experimentally. Under the condition of fiber nutation frequency is 2000Hz and nutation radius is 1.1um, the experimental verification results in our interested range of signal light power (1nW-10nW) meet our design requirements. The receiving field of view (FOV) of tracking system is more than 300urad, and the closed-loop tracking bandwidth (-3dB) is about 115 Hz. When the boresight error is fixed at 80urad, the real calculation error is less than 10%. The closed-loop performance of tracking system is insensitive to the change of signal light power. Our coherent tracking system is of great significance to the inter-satellite beaconless laser communication.