Patent ID: 7389011

Claim:
An optical fiber temperature sensor comprising: a sensing part composed of an optical fiber arranged at a temperature measurement point; a light source injecting a light to the sensing part; a wavelength filter module for branching a Raman scattered light from a back scattered light generated at said sensing part; a photoelectric detector for detecting said Raman scattered light; and a signal processing circuit for processing an electric signal from the photoelectric detector, wherein said light source is a semiconductor laser having a wavelength of 0.78 μm; said wavelength filter module is composed of a longer wavelength side band pass filter for transmitting a Stokes light and a shorter wavelength side band pass filter for transmitting an anti-Stokes light; and the longer wavelength side band pass filter and the shorter wavelength side band pass filter do not allow the light having the wavelength band of said semiconductor laser to be transmitted, a center wavelength of the pass band of said longer wavelength side band pass filter is shifted from the wavelength of the Stokes light toward the longer wavelength side; and a center wavelength of the pass band of said shorter wavelength side band pass filter is shifted from the wavelength of the anti-Stokes light toward the shorter wavelength side.