FREQUENCY OFFSET DETECTING APPARATUS AND METHOD FOR USE IN DIGITAL COHERENT OPTICAL RECEIVER

摘要

PROBLEM TO BE SOLVED: To widen a frequency offset detection range in digital coherent reception.

SOLUTION: An argument difference calculation section (argument computer 301, register 303, subtractor 304) calculates an argument difference of adjacent symbols in an input signal. A subtractor 306 subtracts an output of a loop filter 312 from the calculated argument difference. A 2π/M quantizer 308 performs uniform quantization, at predetermined intervals, upon an output of the subtractor 306. A subtractor 310 subtracts an output of the 2π/M quantizer 308 from the argument difference obtained by the argument difference calculation section. A loop filter 312 averages an output of the subtractor 310.

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