| 摘要 |
PURPOSE:To improve measurement sensitivity and to decrease the number of components by employing an optical system which uses the same interference filters as a light splitting means and a wave-length selecting means. CONSTITUTION:Light from a light source such as a laser is made incident on a 1st interference filter 11 and an end surface of an optical fiber 4 is placed on the optical axis of light with center wavelength lambda0 which is transmitted through the filter. Back scattered light generated in the optical fiber 4 with the incident light is made incident on the 1st interference filter 11 in the opposite from the incident light and light with wavelength which is not nearby the Rayleigh scattered light with the same wavelength lambda0 with the incident light to the optical fiber 4 is reflected by the interference filter 11. A 2nd interference filter 12 is installed on the optical axis of this reflected light. Only anti-Stokes' light is transmitted through the 2nd interference filter 12 and is made incident on a photodetector 9. The photodetected light is converted into an electric signal. Its intensity is measured. Only Stocks' light is transmitted through a 3rd interference filter 13, and photodetected by a photodetector 7 and converted into an electric signal so that the intensity of the anti-Stokes' light is measured.
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