METHOD FOR DETECTING OPTICAL TRANSMISSION LINE LENGTH OF OPTICAL TRANSMISSION DEVICES, AND OPTICAL SIGNAL TRANSMISSION SYSTEM HAVING OPTICAL TRANSMISSION LINE LENGTH-DETECTING FUNCTION

摘要

PROBLEM TO BE SOLVED: To provide a versatile method for detecting an optical transmission line length without requiring special measuring equipment. SOLUTION: A portable child unit 2 can be connected to optical fiber cables 51, 52 coupled to a parent unit 1. When a position detection signal is sent to the optical fiber cable 51 from the parent unit 1, the child unit 2 receives the position detection signal and sends to the optical fiber cable 52. The parent unit 1 calculates a delay time after the position detection signal is sent out before the position detection signal is returned. An optical transmission line length from the parent unit 1 to the child unit 2 is operated based on the delay time. A connection position of the child unit 2 can thus be automatically measured without requiring a special device. The method is widely applicable to optical transmission system having a pair of optical transmission lines for transmitting light signals to opposite directions between the parent and child units, and has sufficient versatility.