To provide a method for manufacturing a sensor element, by which stabilization of an electrode, which is performed prior to inspecting element characteristics, can be performed for a shorter time period and in a more reliable manner than in the conventional. To this end, in the optical amplifier according to the present invention, a delayed phase matching fiber in which a first fiber whose response speed is relatively low is arranged on the input side and a second fiber whose response speed is relatively high is arranged on the output side, is used as the optical amplification medium doped with a rare-earth element. Magnifying means are situated in the path of light to the transducer, and is arranged to magnify the detected image. The base is preferably articulated by a D. Also, a color resin layer is sandwiched between the signal electrodes and the common electrodes. The method comprises steps of generating light by differently colored light emitting diodes and controlling a current flowing through the differently colored light emitting diodes in order to provide the lighting fixture with a desired color temperature.