Abstract: In an optical monitor for monitoring signal lights from a plurality of optical fibers, emission surfaces of the plurality of optical fibers are arranged along a straight line, and a photodetecting surface of a photodetecting element disposed so as to face the emission surfaces is moved in parallel to the straight line along which the emission surfaces are arranged in such manner that light from each of the emission surfaces is received by the photodetecting element, so that the plurality of signal lights are made incident on the photodetecting element successively. The present optical monitor thereby is capable of monitoring a large number of transmission paths while requiring a small number of components.

Abstract: In order to monitor a large number of transmission paths, it is necessary to provide an optical coupling system for each path and dispose a photo detector to monitor the output thereof, or it is necessary to use a means for switching optical coupling. In the former case, there is a problem that the number of components for constituting an optical monitor increases and a signal processing system for monitoring the transmission paths as a whole is complicated. Further, in the latter case, there is another problem that optical coupling has to be maintained whenever the optical path is switched and that a long time is required for inspection when the number of paths is large.