Distributed fiber optic temperature sensing(DTS) system is important in the surveillance of cable temperature.This paper presents the principles of the Raman back-scattering effect based temperature sensing and the OTDR(Optical Time-Domain Reflectometry) based positioning.We take the temperature surveillance system of a 4 km electrical cable of Qingdao as an instance,in which we present the selection of optical cable and system functionalities.Its temperature precision is ±1℃ and location accuracy is ±2 m so it provides the scientific basis for the surveillance of cable temperature and the safety of electric distribution.

The distributed optical fiber temperature measurement approach is superior to other approaches in the thermal extraction of thick oil,which is based on the principles of optical fiber Raman back-scattering and OTDR(Optical Time-Domain Reflectometry) positioning.The experiment of temperature calibration that is performed in an indoor scenario whose temperature is similar to that in a well and by the approach of second fitting to improve temperature accuracy in the range of high temperature,achieves satisfactory results.Its temperature range is from 0 to 350 ℃,the range of optical fiber length from 0 to 1900 m,the temperature accuracy ±2 ℃,and the distance location accuracy ± 2 m,which provides the authentic data for the measurement of the temperature in an oil well.