CLOCK SIGNAL EXTRACT DEVICE AND CLOCK SIGNAL EXTRACT METHOD

摘要

PROBLEM TO BE SOLVED: To extract a clock signal having a frequency of one over an integral number of a bit rate from an optical signal with a high bit rate. SOLUTION: When a modulation signal whose frequency is f1 /n being 1/n of a frequency included in a vicinity frequency area of a circulating frequency of a mode synchronization laser 10 and an input optical signal with a frequency f0 included in the vicinity frequency area are given to the mode synchronization laser 10, a beat signal with a frequency f1 -f0 being a difference between a harmonic component of the modulation signal and the input optical signal is outputted. The beat signal is given to a frequency divider 24, from which a frequency division beat signal(f0 -f1 )/n being 1/n of the frequency is outputted. Then a mixer 26 extracts a clock signal with a frequency f0 /n being frequency division of the frequency of the input optical signal by 1/n as a sum frequency of the frequency division beat signal and a reference signal.