There are various types of rear scattered light, including Rayleigh scattered light, Raman scattered light, and Brillouin scattered light. The AQ8920 uses Raman scattered light, which has the highest temperature dependence among these various light types. The temperature is measured and the scattered light is separated and received. Raman scattered light consists of anti-Stokes light, which occurs at the shorter wavelength end (relative to the wavelength of the light pulse), as well as Stokes light, which occurs at the longer wavelength end. The intensity ratio of these two components changes in proportion to changes in temperature. This characteristic can be used to measure temperature using optical fiber.

Light pulses are input to the measured optical fiber to measure the temperature distribution. The measured optical fiber is a 50/125 É m GI quartz multimode optical fiber.

It may be necessary to study the sheathing's heat withstanding ability and other factors, depending on the temperature environment where the optical fiber is installed, and environmental conditions such as whether the sheathing would be melted by the heat.

Screenshot of measurement display from evaluation software

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