| 摘要 |
PURPOSE:To reduce optical transmission loss of optical fibers due to radiant ray, by automatically controlling increase of said loss by passing laser beam through optical fibers through which optical transmissions are performed. CONSTITUTION:A light generated from a light source 1, such as LED, etc., is transmitted to a photodetector 5 of PiN photodiode, etc., through a directional coupler 2, an optical fiber 3, and another directional coupler 4, and, at the same time, a laser beam from a laser 6, such as YAG laser, is transmitted to another optical fiber 7 through the directional coupler 4, the optical fiber 3 and the directional coupler 2. Since, when a radiant ray falls on the optical fiber 3 and the optical transmission loss increases, the laser beam passing through the optical fiber 3 is absorbed and a heat is generated, and then the optical fiber 3 is heated by the heat, thus, the optical transmission loss is reduced. |
