| 摘要 |
PURPOSE:To monitor the power of an input-output light by a method wherein a light made to branch from an input or an output of a light amplifier by a light-branching unit is passed through a loss medium having no polarization dependence and then sensed by a photosensor and a light-sensing current thereof is monitored. CONSTITUTION:When an input light is inputted to a light-branching unit 2 from an optical fiber 1 on the input side, it is made to branch in such a low branching ratio as about 1/10 and a branch light proceeds to an optical fiber 4 on the monitor side, while a main signal is outputted from an optical fiber 3 on the output side. The branch light signal is attenuated in a loss medium 5 having no polarization dependence and an output thereof is inputted to a light-sensing part 6 and subjected therein to photoelectric conversion, so that an electric signal for monitoring be generated. This signal becomes an output being proportional correctly to the power of the light transmitted to the fiber 1 on the input side. As for the loss medium 5 having no polarization dependence, such a method as to make the axes of cores deviate from each other and to splice them when the end parts of two optical fibers are connected together is used for it. In another method wherein the medium 5 is not used, a loss is given to the light by a loss giving means 7 having no polarization dependence in the light-sensing part 6 and then the light is sensed. |
