Multi-wavelength Brillouin fiber laser based optical fiber temperature sensor

Abstract

A multi-wavelength Brillouin fiber laser based optical fiber temperature sensor which is formed according to an optical fiber Brillouin gain effect, an er-doped optical fiber amplifying effect, a multi-level Brillouin scattering temperature effect and a heterodyning beat frequency demodulation principle comprises a narrow line width single frequency laser, an optical branching device, a polarization controller, an opto-isolator, an optical circulator, a single-mode sensing fiber, an er-doped optical fiber amplifier, an er-doped optical fiber being not pumped, a high-speed photoelectric detector and a frequency analyzer. The multi-wavelength Brillouin fiber laser based optical fiber temperature sensor has the advantages of being many in the number of wavelengths, narrow in line width, fixed in wavelength interval and stable in output. The multi-wavelength Brillouin fiber laser based optical fiber temperature sensor achieves heterodyning best frequency demodulating detection of a high-order stokes wave and high-accuracy high-sensitivity temperature measuring with the single-mode optical fiber which provides gain for the fiber laser being served as a temperature sending detect unit.

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. "A multiplexed 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," Sensors Journal, 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. "A multiplexed 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," Sensors Journal, IEEE, vol.12, no.7, pp.2496-2500, July 2012) used a single-wavelength fiber laser based on fiber grating (FBG), and used the principle that FBG is sensitive to wavelength to construct a temperature sensor based on fiber laser. The sensitivity has every There are still some deficiencies. On the one hand, when the filter is used for demodulation and 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 the 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 this type of laser sensor The measurement accuracy will be limited by the bandwidth of the FBG; also for the distributed multi-point temperature sensor based on the FBG multi-wavelength fiber laser (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, Chen Xiangfei's research group at Nanjing University proposed a A fiber laser sensor based on multi-longitudinal mode (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 , to obtain the ambient temperature value, 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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