| 摘要 |
<p>PURPOSE:To reduce the attenuation of a signal light and improve the accuracy by constituting an optical multiplexer/demultiplexer of a band-pass filter satisfying a specific condition. CONSTITUTION:In the fiber optic distribution-type temperature sensor, a light from a light source is brought into a sensor optical fiber through an optical multiplexer/demultiplexer. A light of a specific wavelength band among a reflecting light of a returning backscattering light is separated by the optical multiplexer/demultiplexer and introduced to a photodetector of a light-measuring system. The optical multiplexer/demultiplexer is constituted to be a band-pass filter separating a Stokes light of a central wavelength lambdas and an anti Stokes light of a central wavelength lambdas a from the backscattering light, featuring that all the conditions according to formulae I-III are satisfied thereby. In the formulae I-III, lambdaa1, lambdas2 indicate a cut-off wavelength of the band-pass band of the Stokes light and, lambdaa1, lambdaa2 show a cut-off wavelength of the band-pass band of the anti Stake light. DELTAlambdas s is a difference of true central wavele of the incident light and the Stokes light, while DELTAlambdaa is a difference of central wavelengths of the incident light and anti Stokes light.</p> |
