What is the working principle of distributed fiber optic temperature measurement in 2024 　　 　　

Fiber optic temperature sensor, Intelligent monitoring system, Distributed fiber optic manufacturer in China

Distributed fiber optic temperature measurement is mainly based on the principles of Raman scattering of light and OTDR of light. The OTDR principle was proposed by Dr. Barnoski in 1977, and Rogers used this technology to achieve distributed temperature measurement in 1980. The OTDR process generates a pulse modulated incident light for the laser and injects it into the fiber. During the process of optical fiber transmission, a portion of the optical energy continuously propagates forward along the fiber transmission medium; Part of it is scattered into the outer layer of the optical fiber or absorbed by the transmission medium system, resulting in transmission loss; Another part of the energy is scattered and transmitted back to the light incident port in the reverse direction. By monitoring the emitted light intensity at the incident port, the scattered light power at various positions of the fiber can be inferred, and the temperature at each position of the fiber can be demodulated through the correlation between scattered light power and temperature, achieving distributed temperature measurement. When the incident pulse light enters the fiber and starts timing, the light scatters from a certain position and returns to the input port. The optical signal received at the incident port of the fiber includes Rayleigh scattered light formed due to fluctuations in the refractive index of the fiber, which is characterized by the same wavelength as the incident light and a higher optical signal intensity; Raman scattering light, which contains anti Stokes and Stokes components; Brillouin scattering, spectral distribution of scattered signals.