| 摘要 |
PURPOSE:To achieve miniaturization and cost reduction, by calculating the wavelength of the incident light from one of the input ports of an optical coupler on the basis of the output ratio of two photodetectors. CONSTITUTION:An optical coupler 1 has two input ports 2a, 2b and two output ports 3a, 3b. Photodetectors 4a, 4b are respectively arranged at places approaching the end surfaces of the output ports 3a, 3b. When the wavelength of certain light is desired to be known, said light is allowed to be incident to the input port 2a and lights are outputted to the output ports 3a, 3b in quantities of a definite ratio. By calculating the ratio of the output of the photodiode 4a to the output of the photodetector 4b by a comparator 5, the wavelength of the incident light is calculated.
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