Scheme for simultaneously measuring strain and temperature by using few-mode FBG-FP

Abstract

The invention provides a scheme for simultaneously measuring strain and temperature by using a few-mode FBG-FP. The scheme comprises a narrow linewidth light source module, a few-mode FBG-FP module, a PDH demodulation module and a feedback control module. Two narrow-linewidth optical fiber light sources with wavelengths corresponding to a few-mode FBG-FP mode are subjected to beam coupling through an optical fiber coupler and then are transmitted backwards, phase modulation is carried out by a straight waveguide modulator, after the two narrow-linewidth optical fiber light sources enter at least mode FBG-FP after passing through an optical fiber circulator, two reflected mode harmonic peaks pass through the optical fiber circulator again and then are separated by a photon lantern, the light enters a photoelectric detector and is converted into an electric signal, PDH error signals in two modes are obtained after the electric signal enters a phase-locked amplification module, and the PDH signals are processed by an FPGA (Field Programmable Gate Array) respectively. According to the scheme, simultaneous measurement of multiple parameters is completed through a single optical fiber, and the sensing characteristic of a few-mode fine grating structure is explored for the first time.

Description

Technical field: [0001] The invention relates to the field of optical fiber sensing, in particular to a scheme for simultaneously measuring strain and temperature by using a few-mode FBG-FP. Background technique: [0002] The few-mode fiber expands the limited mode on the basis of the single-mode fiber, providing a new degree of freedom in the fiber to improve the spectrum utilization of the fiber system. In recent years, few-mode optical fiber has been gradually used in the field of optical fiber communication to expand the transmission bandwidth of optical fiber. However, the application in the field of optical fiber sensing needs to be further studied, and the modulation and demodulation methods for few-mode optical fiber sensing technology need to be changed urgently. [0003] Write fiber Bragg gratings on few-mode fibers to obtain multiple spectral characteristics to realize multi-parameter monitoring. However, the parameter resolution that ordinary few-mode fiber Bragg...

AI Technical Summary

Problems solved by technology

[0003] Write fiber Bragg gratings on few-mode fibers to obtain multiple spectral characteristics to realize multi-parameter monitoring. However, the parameter resolution that ordinary few-mode fiber Bragg gratings can achieve is limited, and the sensing and demodulation methods are not real-time, low Accuracy, such as a torsion sensor based on tilted few-mode fiber grating proposed by Zhang Zuxing et al. (Zhang Zuxing, Gu Changsheng, Zhang Jie, Liu Xinyu. A torsion sensor based on tilted few-mode fiber grating [P]. Jiangsu Province: CN107421469B, 2019 -07-16.) and a gas concentration sensor based on few-mode fiber and Bragg grating proposed by Zhang Weihua et al. (Zhang Weihua, Tong Zhengrong. A gas concentration sensor based on few-mode fiber and Bragg grating [P]. Tianjin : CN106769875A, 2017-05-31.) all use the spectrometer system to monitor the sensing unit, it is difficult to realize the output of real-time sensing information

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