Time comparison system, time comparison device, and time comparison method

Abstract

[Problem] To determine a time difference between clocks which, for example, are placed far apart from each other with high accuracy at low cost. [Solution] In a time comparison system, an intermediate stationdisperses a single optical signalin the spatial region using the optical complex amplitude modulation to simultaneously transmit the optical signalto a plurality of comparative stationsandapart from each other. The intermediate stationtransmits the optical signalwhile changing the transmission angle using phase modulation, performs intensity scanning for the reflected light cof the optical signal, and detects the peak intensity to determine the directions of the comparative stationsand. The reflected light cof the optical signaltransmitted to the comparative stationsandof which the direction have been determined, is detected to determine a round-trip propagation delay time between the intermediate stationand each of the comparative stationsand. The difference calculation unitcalculates a sum of time difference between each of times to and tb associated with the comparative stationsandand the time tc associated with the intermediate station, and the determined propagation delay time to determine time information of each of the comparative stationsand. Based on the result of subtracting, from the time information of the comparative stations, the time information of the comparative stations, the time difference between the comparative stationsandis determined.