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提出并研制了一种结构简单、成本低廉的全光纤型高温-应变组合传感器,其结构是在具有微气泡腔的在线型Fabry-Perot干涉仪(FPI)后级联一个高频CO2激光脉冲写入的长周期光纤光栅(LPFG)。FPI通过采用商用化的熔接机熔接普通单模光纤(SMF)和多模光子晶体光纤(MPCF)形成,两类光纤间的空气泡形成FP干涉腔,由于MPCF具有较大的数值孔径并且其包层具有较大的空气孔,所以MPCF-FPI的干涉条纹具有较大的信噪比和对比度;并且,光纤的表面张力使气泡腔的表面足够光滑,不会降低熔接点的极限强度,从而确保了FPI是一种理想的耐高温应变传感器。高频CO2激光脉冲写入的LPFG能耐800℃高温,且具有较高的温度敏感性。通过分别监测MPCF-FPI和LPFG的波长漂移量,实现应变-高温的同时测量。实验结果表明,本文研制的传感器,其应变灵敏度为2.7 pm/με,温度灵敏度为0.07 nm/℃,可满足实际应用的要求。
An all-fiber high temperature-strain combination sensor with simple structure and low cost was proposed and developed. The structure was fabricated by cascading a high-frequency CO2 laser pulse after the in-line Fabry-Perot interferometer (FPI) with microbubble cavity Into the long-period fiber grating (LPFG). The FPI is formed by welding a common single-mode fiber (SMF) and a multi-mode photonic crystal fiber (MPCF) using a commercially available fusion splicer. The air bubbles between the two types of fibers form the FP interference cavity. Since the MPCF has a larger numerical aperture and its package So that the interference fringes of the MPCF-FPI have a larger signal-to-noise ratio and contrast; and the surface tension of the optical fiber smoothes the surface of the bubble cavity sufficiently without reducing the ultimate strength of the weld, thereby ensuring FPI is an ideal high temperature strain sensor. LPFGs written with high-frequency CO2 laser pulses are resistant to high temperatures of 800 ° C and have a high temperature sensitivity. By simultaneously monitoring the wavelength shift of MPCF-FPI and LPFG, simultaneous measurement of strain-temperature is achieved. Experimental results show that the sensor developed in this paper has a strain sensitivity of 2.7 pm / με and a temperature sensitivity of 0.07 nm / ° C, which can meet the practical application requirements.