| 摘要 |
PURPOSE:To control the photoabsorption quantity by the charge quantity which is energized by providing an electrochromic substance which can control the photoabsorption quantity by the charge quantity which is energized, on a photodetecting window of a photodetector in a photodetecting module, as a means for attenuating a light beam. CONSTITUTION:Between an optical fiber 1 for input and a photodetector 2, and also, on a photodetecting window of the photodetector 2, an element 4 consisting of an electrochromic substance 6, and a circuit 5 for controlling the photoabsorption quantity of this element 4 are provided. As for the electrochromic element 4, an electrochromic substance 6 is inserted and held by transparent electrodes 7, 7 which have been placed in parallel, and by impressing a DC voltage to the transparent electrodes 7, 7 from the electrochromic element control circuit 5, charge is injected into the electrochromic substance 6, and a colored layer is formed. The density of this colored layer increases, when the impressed voltage is boosted, and also, when the polarity of the voltage is inverted, the colored layer is discharged. In such a way, the photoabsorption quantity of the electrochromic element 4 can be changed continuously by the charge quantity which is energized. |
