| 摘要 |
PURPOSE:To stably measure light loss even if a light output varies by measuring the transmitted light power of a body to be measured with modulated light obtained by modulating a light output for measurement and correcting the quantity of variation of the light output according to the quantity of variation of the light output included in the modulated signal. CONSTITUTION:Light from a laser diode is split by a beam splitter 1 into two; and one is made incident on a photodetector provided in a light source part and the other exits from the light source part through an optical system 2 and is made incident on a body to be measured. An output variation component from the laser diode which is contained in the light received by the photodetector is extracted through a low-pass filter and an encoder performs sampling, quantization, and encoding processing. The encoded light output variation information is code-converted into a format suitable to light loss measurement and transmission to a photodetection part, and the driving circuit for the laser diode is operated with the conversion output.
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