The principle of distributed temperature sensing fiber optic temperature measurement
The distributed temperature sensing fiber optic monitoring system is based on distributed fiber optic sensing technology, utilizing the temperature sensitive characteristics of Raman scattering light signals in the fiber optic to achieve accurate measurement of temperature changes. Every point on the temperature sensing fiber can sense and transmit temperature signals. When a strong pulse laser signal is transmitted in the fiber, every point on the fiber will experience weak scattering of the laser signal. The signal intensity of the scattered light is a certain function of the temperature at that point. By detecting the intensity of the scattered light at each point, the temperature at that point can be calculated, and the temperature distribution on the entire fiber can be obtained. When light pulses propagate along optical fibers, various types of radiation scattering are generated, mainly including Rayleigh scattering, Brillouin scattering, and Raman scattering. Among them, Rayleigh reflected light has no fixed relationship with temperature changes, and temperature distribution cannot be calculated based on the characteristics of reflected light; Raman scattering light is more sensitive to temperature changes; Brillouin scattering light is sensitive to both temperature and strain. Due to the similar characteristics of Brillouin scattering and Rayleigh scattering, the spectral similarity is high, making it difficult to separate them through filters. At the same time, Brillouin scattering is sensitive to stress and strain. Therefore, using Raman scattering to achieve temperature sensing is the most commonly used technical means.
The fire warning and temperature monitoring of subway tunnels are directly related to personal safety and public property safety. The linear fiber optic temperature sensing fire detection system can prevent accidents and ensure the safe and energy-saving operation of the subway system by real-time online detection of tunnel temperature and before a fire occurs.
Temperature sensing optical fiber is an important component of subway tunnel temperature detection. Tunnel temperature sensing optical fiber generally uses armored optical fiber, which is wrapped with a layer of metal armor on the outside of the optical fiber to protect the fiber core inside, and make the optical fiber have strong pressure and tensile resistance, which can prevent rodent bites and moisture.
The distributed temperature sensing fiber optic fire warning system includes modules such as temperature sensing fiber optic, photoelectric signal conversion, and signal processing warning. When in use, temperature changes cause changes in the optical signal inside the temperature sensing fiber. Through the conversion of photoelectric signals and information processing, real-time temperature monitoring and fire warning can be achieved. Temperature sensing optical fiber is an important component of fire warning systems.
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