| 摘要 |
<p>PURPOSE:To measure temperature with high reliability even if an undesired influence is exerted upon an optical fiber by branching back scattered light into plural light components, and measuring the temperature with one branch output light beam and correcting variation with the other one. CONSTITUTION:The pulse light from a light source 1 is made incident on the optical fiber 3 through an optical switch 2. The back scattered light from scattered light from respective parts of the optical fiber 3 travels back to the light source 1. This back scattered light is guided to an optical branch device 4 through the switch 2. The branch device 4 branches the light in two directions and one light beam is guided to a photodetecting element 6 through a filter 5 with wavelength for transmitting anti-Stokes light. The other light beam is guided to a photodetecting element 6' through a filter 5' with wavelength for transmitting Rayleigh scattered light. The outputs of those elements 6 and 6' are supplied to a comparator 7, which compares both intensity values to correct transmission loss which is not under the influence of temperature like the bending of the halfway path of the optical fiber 3.</p> |
