Method and system for optical timing transfer

A system for generating a timing signal that is transmitted from a base station to a remote station via an optical fiber,

• the base station including:
• a timing signal generation unit configured to generate the timing signal and supply the generated timing signal to a microwave modulator and a timing comparison unit;
• a microwave generator configured to generate a first reference microwave signal having a first carrier frequency and supply the generated first reference microwave signal to a microwave modulator;
• a microwave modulator configured to generate a forward-path microwave phase modulation signal by phase-modulating the first reference microwave signal by using the timing signal, and supply the generated forward-path microwave phase modulation signal to an optical intensity modulator;
• a first laser light source configured to generate a first laser optical signal having a wavelength λ1 and supply the generated first laser optical signal to the optical intensity modulator;
• an optical intensity modulator configured to generate a forward-path optical intensity modulation signal by optical intensity-modulating the first laser optical signal by using the forward-path microwave phase modulation signal, and supply the generated forward-path optical intensity modulation signal to a directional coupler;
• a directional coupler configured to supply the forward-path optical intensity modulation signal to the remote station via the optical fiber, separate a backward-path optical intensity modulation signal, which is supplied from the remote station via the optical fiber, from the forward-path optical intensity modulation signal, and supply the separated backward-path optical intensity modulation signal to a photoelectric convertor;
• a photoelectric convertor configured to perform photoelectric conversion on the backward-path optical intensity modulation signal and extract a backward-path microwave phase modulation signal, and supply the extracted backward-path microwave phase modulation signal to a microwave demodulator;
• a microwave demodulator configured to extract a round trip timing signal from the backward-path microwave phase modulation signal, and supply the extracted round trip timing signal to a timing comparison unit;
• a timing comparison unit configured to determine a transmission delay from a timing difference between the timing signal and the round trip timing signal and notify a control unit of the determined transmission delay;
• and
• the control unit configured to perform control, based on the transmission delay, and
• the remote station including:
• a directional coupler configured to separate the forward-path optical intensity modulation signal, which is supplied from the base station via the optical fiber, from the backward-path optical intensity modulation signal, and supply the separated forward-path optical intensity modulation signal to a photoelectric convertor, and supply the backward-path optical intensity modulation signal to the remote station via the optical fiber;
• a photoelectric convertor configured to perform photoelectric conversion on the forward-path optical intensity modulation signal and extract the forward-path microwave phase modulation signal, and supply the extracted forward-path microwave phase modulation signal to a backward-path microwave phase modulation signal generation unit;
• a backward-path microwave phase modulation signal generation unit configured to generate a backward-path microwave phase modulation signal having a second carrier frequency, which is different from the first carrier frequency, by using the forward-path microwave phase modulation signal, and supply the generated backward-path microwave phase modulation signal to an optical intensity modulator;
• a second laser light source configured to generate a second laser optical signal having the wavelength λ1 and supply the generated second laser optical signal to the optical intensity modulator;
• and
• an optical intensity modulator configured to generate the backward-path optical intensity modulation signal by optical intensity-modulating the second laser optical signal by using the backward-path microwave phase modulation signal, and supply the generated backward-path optical intensity modulation signal to the directional coupler, wherein
• the control unit controls the timing signal generation unit, and generates the timing signal for the remote station by advancing the timing signal by an amount of the transmission delay.