| 摘要 |
<p>PROBLEM TO BE SOLVED: To lengthen a measurement distance by placing optical fibers so that natural Raman scattered light generation efficiency of the optical fibers increases as the fiber comes farther from a pulse light incident side. SOLUTION: Optical fibers 11 to in for a sensor are fused so that their Raman scattered light generation efficiencyηi (i=1, 2, 3...n) successively increases asη1<η2<η3<...<ηn as the fiber comes farther from a temperature sensor unit 1. When pulse light enters the optical fiber temperature sensor, propagating pulse light attenuates as it comes farther from an incident end, but since the fibers are connected so that Raman scattered light generation efficiencyηi successively increases, Raman scattered light intensity scattered from a distant place far from the pulse light incident end may not weaken remarkably. Therefore, without improving sensitivity or a dynamic range of a light receiver, back Raman scattered light signal can be observed over a long distance.</p> |
