摘要
用栅区仅为1 mm、间隔仅为20 mm的超短光纤光栅串,借助激光焊接工艺制作出长度约为40 mm,直径约为20 mm的基于弹性膜片增敏的带温补结构的光纤光栅压力传感器,用于海洋深度探测。在0.6 MPa测量范围内,传感器的理论压力灵敏度为-1.218 nm/MPa,利用有限元分析法仿真得到的压力灵敏度为-1.364 nm/MPa,通过温度及压力测试实验消除温度对测压光纤光栅的影响后得到传感器实际平均压力灵敏度达-1.728 nm/MPa,升降压曲线的线性度达99.9%。与激光密封尾纤方式相比,采用环氧胶密封尾纤不必考虑瞬时高温对光纤造成的损伤,且更容易保持对光纤所施加的预应力。结合仿真分析发现双光纤光栅温度响应趋势存在差异是由结构设计的缺陷所致,后续可对此进行改进。在传感器的制作过程中增设了温度及压力老化步骤,可有效提高传感器升降压曲线的线性度及重合度。尾纤抖动会对传感器稳定性造成影响,建议使用切趾光纤光栅或设置缓冲区的方法解决。环氧胶固化时流动导致光纤光栅有效长度减小以及预应力增加使光纤光栅压力灵敏度提高,是实测传感器压力灵敏度偏高的主要原因。
For the field of ocean depth detection,a small volume diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is made.The length and diameter of the fiber Bragg grating pressure sensor are approximately 40 mm and 20 mm,respectively.The diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure uses an ultrashort fiber Bragg grating string.There are two fiber Bragg gratings on the ultrashort fiber Bragg grating string.The length of the two fiber Bragg gratings is 1 mm,and the interval between them is 20 mm.One fiber Bragg grating is used to measure pressure,and the other fiber Bragg grating is only affected by temperature,which can eliminate the influence of temperature on the pressure measuring fiber Bragg grating.The optical fiber is encapsulated in a metal tube a short distance away from the measuring pressure fiber Bragg grating.The end of the metal tube is fixed on the elastic metal diaphragm by a laser welding process.In this way,the optical fiber and metal diaphragm are not fixed by epoxy adhesive directly,which can avoid the influence of aging and creep of epoxy adhesive on the performance of the diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure.In the measuring range of 0.6 MPa,the theoretical pressure sensitivity of the diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is-1.214 nm/MPa,and the pressure sensitivity of the diaphragmtype fiber Bragg grating pressure sensor with a temperature compensation structure obtained by the finite element analysis method is-1.364 nm/MPa.After the diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is fabricated,the pressure and temperature characteristics of the sensor are tested.With the help of a fiber Bragg grating only affected by temperature,the influence of temperature on the pressure measuring fiber Bragg grating is eliminated through calculation.The actual average pressure sensitivity of the diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is-1.728 nm/MPa.Moreover,the linearity of the boost and buck curves of the diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is more than99.9%,and the boost and buck curves of the diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure also coincide well.In addition,the best way of the tail fiber seal,the reason of the different temperature response characteristics of the double fiber grating,the method of improving the linearity and coincidence degree of the pressure curve,the reason and solution of affecting the stability of the sensor,and the reason of improving the sensitivity of the measured pressure are discussed.First,when the thickness of the metal tube that encapsulates the optical fiber is relatively thin,comparative experiments show that the method of sealing the fiber tail with epoxy glue is better than laser welding.By sealing the fiber tail with epoxy glue,the wavelength shift of the fiber Bragg grating can reach2 nm.It can be seen that sealing the tail of the optical fiber with epoxy glue more easily maintains the prestress applied to the optical fiber.Second,a temperature response test experiment of a diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is carried out.The experimental results show that the temperature response of the fiber Bragg grating and pressure response of the fiber Bragg grating are slightly different.Combined with the simulation analysis,it is found that the main reason for the difference in the temperature response trend of dual fiber Bragg gratings is the defect of the structural design.Third,to improve the linearity and coincidence of the boost and buck curves of the sensor,temperature and pressure aging processes are added to the sensor manufacturing process.The experimental results show that these methods are effective.Next,considering the influence of an optical fiber tail wobble on the stability of a diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure,it is suggested to use apodisated linearly chirped fiber gratings or set up a region to isolate external forces to solve the problem.Finally,the problem that the actual pressure sensitivity of a diaphragm-type fiber Bragg grating pressure sensor with a temperature compensation structure is higher than the theoretical value is discussed from several angles.The main reasons are that the effective length of the fiber Bragg grating decreases due to the flow of epoxy glue and the pressure sensitivity of the fiber Bragg grating increases due to the increase in prestress.
作者
于璐瑶
赵强
杜大伟
曲轶
YU Luyao;ZHAO Qiang;DU Dawei;QU Yi(Hainan Key Laboratory of Laser Technology and Optoelectronic Functional Materials,School of Physics and Electronic Engineering,Hainan Normal University,Haikou 571158,China;Institute of Oceanographic Instrumentation,Qilu University of Technology(Shandong Academy of Sciences),Qingdao,Shandong 266061,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2022年第3期237-245,共9页
Acta Photonica Sinica
基金
海南省重大科技计划(No.ZDKJ2019005)
国家重点研发计划(No.2018YFF01014101)
国家自然科学基金(Nos.61864002,61964007,61933004)
山东省自然基金面上项目(No.ZR2019MF022)
山东省军民融合项目(No.2019JMRH0105)
海南省重点研发项目(Nos.ZDYF2020020,ZDYF2020036,ZDYF2020217)
中国工程科技发展战略项目(No.19-HN-XZ-07)
海南省基础与应用基础研究计划(自然科学领域)高层次人才项目(Nos.2019RC190,2019RC192)
海南省高等学校科学研究项目(Nos.Hnky2020-24,Hnky2020ZD-12)
海南省院士创新平台科研专项项目(No.YSPTZX202034)。
关键词
光纤光栅
压力传感器
有限元分析法
弹性膜片
海洋
Fiber Bragg grating
Pressure sensor
Finite element analysis method
Elastic diaphragm
Ocean