PURPOSE: To make reliability high and handling easy by dividing the overall length of plural optical transmission lines to ≥2 parts, and coupling the optical transmission lines on a light source side and a photodetector side optically in the coupling part between at least one optical transmission line.
CONSTITUTION: For example, the rays from three light emitting diodes 1 are transmitted through optical fibers or optical fiber bundles 21, and after the rays are once condensed, mixed and separated with an another optical transmission line 5, the rays are again transmitted to optical fibers or optical fiber bundles 22 and are supplied to the three light firing thyristors 3 which are connected in series. Here, even when the output of one diode 1 among the three diodes decreases, the line 5 which mixes the rays supplies the rays of the remaining two normal diodes 1 to the respective light firing thyristors after mixing the rays, thus making the firing of all the light firing thyristors possible with the two light emitting diodes and providing stability in their switching operation.
KONISHI NOBUTAKE
TANAKA TOMOYUKI
