Optical fiber temperature sensor based on multi-wavelength Brillouin fiber laser

Abstract

A fiber temperature sensor based on multi-wavelength Brillouin fiber laser is made by using the Brillouin gain effect of fiber, the amplification effect of erbium-doped fiber, the temperature effect of multi-level Brillouin scattered light and the principle of heterodyne beat frequency demodulation Fiber optic temperature sensors, including narrow-linewidth single-frequency lasers, optical splitters, polarization controllers, optical isolators, optical circulators, single-mode sensing fibers, Erbium-doped fiber amplifiers, unpumped Erbium-doped fibers, high-speed optoelectronics detectors, spectrum analyzers. The invention has the advantages of large number of wavelengths, narrow line width, fixed wavelength interval, and stable output. The single-mode fiber provided for the gain of the fiber laser is used as a temperature sensing detection unit to perform heterodyne beat frequency resolution on high-order Stokes waves. Adjust the detection to achieve high-precision and high-sensitivity temperature measurement.

Description

technical field [0001] The present invention relates to optical fiber laser sensors, especially including narrow linewidth single-frequency lasers, optical splitters, polarization controllers, optical isolators, optical circulators, single-mode sensing fibers, erbium-doped fiber amplifiers, unpumped doped Erbium fiber optics, high-speed photodetectors, spectrum analyzers, fiber optic temperature sensors based on multi-wavelength Brillouin fiber lasers. Background technique [0002] In the field of sensors based on fiber lasers, domestic and foreign scholars (A. T. Alavie, et. al. "Amultiplexed Bragg grating fiber laser sensor system," IEEE Photon. Technol. Lett., vol. 5, no. 9, pp. 1112–1114 , Sep. 1993; invention patent proposed by Xu Tuanwei et al., authorized publication number: CN102829810A; Ahmad, H.; et. al.. "Temperature Sensing Using Frequency Beating Technique From Single-Longitudinal Mode Fiber Laser," SensorsJournal, IEEE, vol.12 , no.7, pp.2496-2500, July 2012) ...

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Problems solved by technology

[0002] In the field of sensors based on fiber lasers, domestic and foreign scholars (A. T. Alavie, et. al. "Amultiplexed Bragg grating fiber laser sensor system," IEEE Photon. Technol. Lett., vol. 5, no. 9, pp. 1112–1114 , Sep. 1993; invention patent proposed by Xu Tuanwei et al., authorized publication number: CN102829810A; Ahmad, H.; et. al.. "Temperature Sensing Using Frequency Beating Technique From Single-Longitudinal Mode Fiber Laser," SensorsJournal, IEEE, vol.12 , no.7, pp.2496-2500, July 2012) Using a single-wavelength fiber laser based on a fiber grating (FBG), using the principle of FBG's sensitivity to wavelength, a temperature sensor based on a fiber laser was constructed, with a sensitivity of GHz per degree Celsius Level changes, but there are still some shortcomings. On the one hand, when the filter is used for demodulation detection, it is affected by the adjustable speed of the filter, which not only increases the complexity of the system but also reduces the response speed of the system. On the other hand, When using beat frequency demodulation detection, a single-frequency light source matching the output of this fiber laser is required as a reference, which not only increases the cost, but also is not suitable for high temperature detection. The third aspect is that the measurement accuracy of this type of laser sensor will be reduced. Limited by the bandwidth of the FBG; also for distributed multi-point temperature sensors based on FBG multi-wavelength fiber lasers (R. Perez-Herrera, et. al.. "L-Band Multiwavelength Single-Longitudinal Mode Fiber Laser for Sensing Applications," J. Lightwave Technol. 30, 1173-1177,2012.) There will also be the first and third problems of single-wavelength fiber lasers; in order to solve the first two problems, the research group of Chen Xiangfei of Nanjing University proposed a multi-vertical Mode fiber laser sensor (Zuowei Yin; et. al.. "Fiber Ring Laser Sensor for Temperature Measurement," Lightwave Technology, Journal of , vol.28, no.23, pp.3403,3408, Dec.1, 2010 ; S. Liu, et. al..Multilongitudinal mode fiber laser for strain measurement, Opt. Lett. 35,835-837, 2010.), through the detection of the fundamental frequency of the fiber laser and the beat frequency of different order longitudinal modes, the ambient temperature value is obtained , but since the mechanism of this temperature sensor is to sense the thermal effect of the optical fiber itself, even if the longitudinal mode is 76 times the fundamental frequency, its sensitivity only changes in the order of kHz per degree Celsius

[0003] The above-mentioned fiber laser sensors cannot realize high-precision and high-sensitivity temperature measurement at the same time, so it is urgent to develop a high-precision and high-sensitivity fiber optic temperature sensor

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