Distributed Temperature Sensing System (DTS), which uses advanced OTDR technology and Raman scattered light to be sensitive to temperature, detects temperature changes at different positions along the fiber, and achieves truly distributed measurements. In addition to timely warning of fire hazards, the linear optical fiber differential fixed temperature fire detector can also accurately locate the fire location. As a mature distributed temperature measurement method, the linear optical fiber differential fixed temperature fire detector has the advantages of long measurement distance, high measurement accuracy, fast response speed, anti-electromagnetic interference, and suitable for flammable and explosive dangerous places, etc., and can be widely used. It is used in high-voltage cable online monitoring, power carrying capacity analysis, traffic tunnel fire monitoring, oil and gas storage tank fire monitoring, coal conveying belt fire monitoring, dam leakage monitoring and other fields.
The temperature measurement of DTS is based on the spontaneous Raman scattering effect. After the high-power narrow-pulse-width laser pulse LD is incident on the sensing fiber, the laser interacts with the fiber molecules to generate extremely weak backscattered light. The scattered light has three wavelengths, namely Rayleigh (Rayleigh) and anti-stokes (anti-stokes). Stokes) and stokes (Stokes) light; among them, the anti-stokes temperature is sensitive, it is the signal light; the stokes temperature is not sensitive, it is the reference light. The backscattered signal light from the sensing fiber passes through the beam splitter module WF again, isolates the Rayleigh scattered light, transmits the temperature-sensitive anti-stokes signal light and the temperature-insensitive stokes reference light, and is received by the same detector (APD) , and the temperature can be calculated according to the ratio of the light intensity of the two. The determination of the position is based on the optical time domain reflectometry OTDR technology, and the position of the optical fiber corresponding to the scattered signal can be determined by measuring the echo time of the scattered signal by using high-speed data acquisition.