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.