[Problem] To inexpensively and highly accurately determine the time difference between clocks disposed so as to be separated in remote areas, or the like. [Solution] In this time comparison system 20, an intermediary station 21 uses optical complex amplitude modulation to disperse a single optical signal 21c in the spatial domain and simultaneously transmits the optical signal 21c to a plurality of separated comparison stations 22, 23. The intermediary station 21 transmits the optical signal 21c while changing the transmission angle through phase modulation, scans the intensity of the resulting reflected light c1, detects peak intensities, and identifies the directions of the comparison stations 22, 23. The intermediary station 21 detects the optical signal 21c that has been transmitted to the identified comparison stations 22, 23 and reflected back as reflected light c1 and determines the round-trip propagation delay times between the intermediary station 21 and comparison stations 22, 23. A difference computation unit 25 obtains time information for the comparison stations 22, 23 by adding the determined round-trip propagation delay times to the time differences between the times ta, tb of the comparison stations 22, 23 and the time tc of the intermediary station 21. The time difference between the comparison stations 22, 23 is determined from the result of subtracting, from the time information for one comparison station 22, the time information for the other comparison station 23.
展开▼
