A High-dynamic Wavelength Tracking and Millimeter-level Ranging Inter-satellite Laser Communication Link with Feedback-Homodyne Detection

The Integrated Laser Communication/Ranging System, which uses coded signal as the ranging information carrier, is of great importance to the next large-capacity inter-satellite information network. In this paper, a system design with high-sensitivity feedback-homodyne detection scheme and asynchronous ranging algorithm is demonstrated with real-time FPGA implementation. The parallel FFT estimation is applied to improve the speed and range of wavelength drift tracking, which can handle dynamic wavelength drift up to 2.4 pm/s (300 MHz/s). Meanwhile, for clock sources with subtle dynamic frequency offset and sufficient stability, the proposed fractional symbol ranging method is proven to achieve millimeter-level measurement accuracy. The designed system is shown to perform well in terms of both laser linewidth tolerance and noise resistance