DIGITAL COHERENT RECEIVER, OPTICAL SPACE COMMUNICATION SYSTEM, AND DOPPLER SHIFT CAPTURING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To always input a significant sample string for digital signal processing for a large amount of Doppler shift, and stably perform initial capture of Doppler shift compensation by the digital signal processing and recovery from signal interruption at high speed.;SOLUTION: A digital coherent reception unit 1 includes: an ADC 15 that performs AD conversion of an electric signal generated by performing coherent detection of a received optical signal by using local oscillator light; an intensity monitor 17 that detects intensity of a signal output from the ADC 15; and a plural frequency generation unit 13 that generates a plurality of frequency components set to a number needed to cover the range of a Doppler shift that might occur to the local oscillator light at a frequency interval corresponding to the band of the ADC if the intensity of the signal is below a threshold value.;SELECTED DRAWING: Figure 1;COPYRIGHT: (C)2017,JPO&INPIT