Fiber optic related technology enables us to measure temperature distribution along entirelength of optical fiber over several kilometers. This newly developed system is completelydifferent from conventional electrical sensors in that it uses optical fiber itself as a sensor. Thesystem measures temperature distribution by detecting Raman scattered light intensity usingoptical time domain reflectometry-OTDR-method.
In this paper, we first explain principle of this unique sensing system, and then discuss relationbetween the system's performance and performance of laser light source which is one ofthe most important devices of the system. Also experimental results are shown for each applicablelasers. It became clear that a system using 850nm laser diode is effective for short distancemeasurement while high power, longer wavelength light source must be engaged to measurelonger distance.