摘要
针对在多腔型法布里-珀罗传感器中难以提取动态信号的问题,提出了一种用于多腔型法布里-珀罗传感器的三波长解调技术。该解调技术使用放大自发辐射光源和三个固定中心波长的宽带光纤滤波器,使干涉现象仅发生在多腔型光纤法布里-珀罗传感器的短腔中,以此提取较短腔的三个干涉信号。建立了校正算法和反正切算法来提取振动信号。实验结果表明,该解调技术成功提取了频率为1 kHz、峰峰值幅度为2.6μm的振动信号。解调速度为500 kHz,解调分辨率为0.25 nm。该解调技术具有系统紧凑、成本低、速度快、鲁棒性高等优点,在多腔型法布里-珀罗传感器方面有巨大的潜力。
Fiber-optic Fabry-Pérot sensors have a wide range of applications,including aerospace,largescale construction,oil collection,and many other fields.In many cases,dynamic parameters,such as dynamic pressure,vibration,acoustics,and ultrasonics are required to be measured.In order to measure these parameters,a variety of fiber-optic Fabry-Pérot sensors are produced.In some fields,the multicavity fiber-optic Fabry-Pérot sensor is inevitable for some advantages.For example,in the field of aerospace engine testing,dynamic pressure is a key parameter that often needs to be measured,and the micro-electro-mechanical system external Fabry-Pérot interferometer pressure sensors with multiple Fabry-Pérot cavities are often designed for aerospace engine pressure measurement due to their consistency and airtightness.Moreover,multi-cavity Fabry-Pérot sensors are good candidates for multi-parameter measurements.The different Fabry-Pérot cavities with different lengths are used to measure different parameters to achieve multi-parameter measurement.Therefore,multi-cavity Fabry-Pérot sensors are becoming increasingly important in engineering applications.However,extracting dynamic signals in multicavity Fabry-Pérot sensors is a challenge.In this paper,an improved passive three-wavelength phase demodulation technology based on a broadband light source is proposed for dynamic interrogation of the shortest cavity in a multi-cavity Fabry-Pérot sensor.According to the principle of low coherence interference,when the optical path difference introduced by the Fabry-Pérot interferometer is less than the coherent length received by the photodetectors,interference occurs.In contrast,when the optical path difference introduced by the Fabry-Pérot interferometers is longer than five times the coherence length,the interference phenomenon becomes insignificant and it can be considered that the interference disappears.Therefore,a flat-top amplified spontaneous emission light source and three broadband fiber filters were used to ensure the interference only occurs in the short cavity.The quadrature signals are obtained by three filtered optical signals with arbitrary cavity length using an improved phase calibration algorithm.The established signal calibration algorithm allows the demodulation technology for arbitrary short cavity lengths and arbitrary central wavelength.The demodulation technology can work without the direct-current voltages,so the demodulation system can reduce the fiber-optic disturbance noise.The arctangent algorithm is established to extract vibration signals by the quadrature signals.Compared with the previous phase calibration algorithm,the phase calibration algorithm proposed in the paper is more concise.The experimental system was consisted of a reflective bracket,a light source,a multi-cavity Fabry-Pérot interferometer,a fiber-optic coupler,three fiber filters,three photodiodes,an analog-to-digital conversion and a personal computer.The light from the light source passed through the fiber-optic coupler to the multi-cavity Fabry-Pérot interferometer.A multi-cavity Fabry-Pérot interferometer consists of a gradient-index lens and a 300-μm-thick double-polished quartz glass fixed on a piezoelectric transducer.The light reflected from the interferometer passed through the coupler and through the filters to the photodiodes.Three interferometric signals at each center wavelength were obtained using three photodiodes.The voltage signals were collected by analog-to-digital conversion and transmitted to a personal computer.The feasibility of the demodulation algorithm was verified by simulations and experiments.The experimental results show that the vibration signals with a frequency of 1 kHz and peakto-peak amplitude of 2.6μm is successfully extracted with different Fabry-Pérot cavity length,which proves that the three-wavelength demodulation algorithm can be used for optical fiber multi-cavity Fabry-Pérot sensor with arbitrary short cavity length.The demodulation speed is 500 kHz and the demodulation resolution is 0.25 nm.The demodulation technology makes it possible to extract dynamic signals in a multicavity Fabry-Pérot sensor.If the spectrometer is used at the same time,the dynamic signal measured by the short cavity and the static signal measured by the long cavity can be interrogated at the same time.This demodulation technology has the advantages of a compact system,low cost,fast speed and high robustness,illustrating its bright potential for multi-cavity Fabry-Pérot sensors.
作者
任乾钰
贾平岗
钱江
王军
刘文怡
熊继军
REN Qianyu;JIA Pinggang;QIAN Jiang;WANG Jun;LIU Wenyi;XIONG Jijun(State Key Laboratory of Dynamic Measurement Technology,North University of China,Taiyuan 030051,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2022年第9期188-197,共10页
Acta Photonica Sinica
基金
国家自然科学基金(Nos.51935011,52075505)
国家自然科学基金创新研究群体项目(No.51821003)
国家重大科技专项(No.J2019-V-0015-0110)。
关键词
法布里-珀罗腔
光纤传感器
三波长解调算法
低相干干涉
腔长解调
Fabry-Pérot cavity
Fiber optics sensor
Three-wavelength demodulation algorithm
Low coherence interference
Cavity length interrogation
