| 摘要 |
PROBLEM TO BE SOLVED: To obtain a video supervisory system where a state of a video image after optical conversion can be confirmed while staying at a center unit without the need for visit to a transmission line. SOLUTION: After an O/E conversion section 21 of an optical node unit 2 converts an optical video signal into an electric signal, an outgoing signal branching device 22 branches the electric signal and the passing side video signal is sent to a CATV coaxial transmission line through a filter 24, and the branch side video signal is fed to a band pass filter 24. The band pass filter 23 cuts off frequencies at the outside of a prescribed frequency band of the branch side video signal to allow a loopback video signal to pass through an incoming single branching device 25. The incoming single branching device 25 inserts the loopback video signal to an incoming signal from the CATV coaxial transmission line and the resulting signal is given to an E/O conversion section 26. The E/O conversion section 26 converts the incoming signal from the incoming single branching device 25 into an optical signal, which is outputted to the optical transmission line and a supervisory television receiver 3 displays the loopback video image converted into an electric signal by an O/E conversion section 12. |
