WO2020125517A1 - 基于光纤布拉格光栅法布里-泊罗腔的传感装置 - Google Patents

基于光纤布拉格光栅法布里-泊罗腔的传感装置 Download PDF

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WO2020125517A1
WO2020125517A1 PCT/CN2019/124598 CN2019124598W WO2020125517A1 WO 2020125517 A1 WO2020125517 A1 WO 2020125517A1 CN 2019124598 W CN2019124598 W CN 2019124598W WO 2020125517 A1 WO2020125517 A1 WO 2020125517A1
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bragg grating
fiber
perot cavity
fabry
device based
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French (fr)
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张亮
董玉明
焦国华
鲁远甫
陈巍
吕建成
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中国科学院深圳先进技术研究院
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre

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  • the invention relates to the field of sensing technology, in particular to a sensing device based on fiber Bragg grating Fabry-Perot cavity.
  • optical fiber sensors are particularly suitable for sensing applications in flammable, explosive, and strong electromagnetic fields due to their inherent safety characteristics. They can be convenient, accurate, and effective for various environments, especially various harsh Detection of physical quantities in the environment.
  • Fiber Bragg Grating (Fiber Bragg Grating, FBG) sensor's central peak wavelength is usually related to the temperature and strain to which it is subjected. Therefore, according to this principle, fiber grating can be made into fiber grating temperature sensor and fiber grating strain sensor.
  • FBG-FP fiber Bragg grating Fabry-Perot cavity
  • Fiber Bragg grating Fabry-Perot cavity is to write two Bragg gratings with the same parameters in two places separated by a certain distance in the fiber core.
  • the optical signal of a certain wavelength that meets the reflection conditions of the grating is incident, it will be Coupled to reflect and transmit light waves, so that the light waves oscillate between the two gratings, forming multi-beam interference, thereby forming high-precision interference fringes in the reflection band of the Bragg grating.
  • the basic principle of using a fiber Bragg grating Fabry-Perot cavity for physical quantity sensing is that changes in physical quantities such as temperature and strain will cause the cavity length of the Fabry-Perot cavity formed between the two gratings to change, resulting in interference fringes
  • the characteristic wavelength (transmission peak wavelength or reflection peak wavelength) drifts. Due to the small 3dB bandwidth of the transmission peak and reflection peak, it can accurately measure a small wavelength drift. Its sensitivity is equivalent to that of the FBG sensor, but it can improve the measurement accuracy. .
  • the current FBG-FP sensor improves the wavelength demodulation accuracy compared to the FBG sensor, its improvement space is also limited by the resolution of the demodulation device.
  • the demodulation mode of the spectrometer In the demodulation mode of the spectrometer, it can reach 10pm. Under light source demodulation, it can only reach 1pm, the corresponding strain sensitivity is at the level of micro-strain, and the temperature sensitivity is 0.1 degrees Celsius, which cannot meet higher requirements, such as earth tide measurement and earthquake precursor observation. Therefore, how to further improve the accuracy of FBG-FP sensor measurement is a problem that the industry has been exploring and solving.
  • the present invention provides a sensing device based on a fiber Bragg grating Fabry-Perot cavity, which can obtain interference fringes with a larger free spectral range, achieve higher sensitivity, and thus improve transmission Sensory measurement accuracy.
  • a sensing device based on a fiber Bragg grating Fabry-Perot cavity includes a light source unit, a fiber circulator, a fiber sensing unit and a spectrum detection unit, the light source unit is connected to the first port of the fiber circulator , The optical fiber sensing unit is connected to the second port of the optical fiber circulator, and the spectrum detection unit is connected to the third port of the optical fiber circulator, wherein the light source unit includes an active mode-locked laser, the The optical fiber sensing unit is a fiber Bragg grating Fabry-Perot cavity, the equivalent optical path of the active mode-locked laser is n 1 L 1 , and the equivalent optical path of the fiber Bragg grating Fabry-Perot cavity The difference is 2n 2 L 2 ; where, i is a positive integer,
  • n 1 is the equivalent refractive index of the laser cavity of the active mode-locked laser
  • L 1 is the equivalent cavity length of the laser cavity of the active mode-locked laser
  • n 2 is the fiber Bragg grating Fabry-
  • the equivalent refractive index of the Poro cavity L 2 is the equivalent cavity length of the fiber Bragg grating Fabry-Perot cavity
  • ⁇ is the reflection of the fiber Bragg grating in the fiber Bragg grating Fabry-Perot cavity
  • the center wavelength, ⁇ is the reflection bandwidth of the fiber Bragg grating in the fiber Bragg grating Fabry-Perot cavity.
  • the value range of k is:
  • the value range of i is: 1 ⁇ i ⁇ 5.
  • the equivalent refractive index n 2 and the equivalent cavity length L 2 of the fiber Bragg grating Fabry-Perot cavity satisfy the conditions:
  • the optical fiber sensing unit includes a first high inverse Bragg grating and a second high inverse Bragg grating written into the optical fiber, the first high inverse Bragg grating and the second high inverse Bragg grating have the same
  • the structural parameters and the mutual arrangement are arranged to constitute the fiber Bragg grating Fabry-Perot cavity.
  • the reflection bandwidth ⁇ of the first high inverse Bragg grating and the second high inverse Bragg grating is 0.2 nm or more, and the reflectance is 60% or more.
  • the reflectances of the first high inverse Bragg grating and the second high inverse Bragg grating are respectively 90% or more.
  • the active mode-locked laser is an active mode-locked fiber laser.
  • the light source unit further includes an optical fiber isolator and a linear polarizer, and the laser light output by the active mode-locked laser sequentially passes through the optical fiber isolator and the linear polarizer and is input to the first of the optical fiber circulator port.
  • the active mode-locked fiber laser, fiber isolator, linear polarizer, fiber circulator, and fiber Bragg grating Fabry-Perot cavity are all single-mode fiber devices.
  • the sensor device based on the fiber Bragg grating Fabry-Perot cavity uses an active mode-locked laser as the signal light source, and sets the equivalent optical path n 1 L 1 of the active mode-locked laser to be close to
  • the equivalent optical path difference of the fiber Bragg grating Fabry-Perot cavity is an integer multiple of 2n 2 L 2 (or the laser pulse period of the control laser is close to the oscillation period of the fiber Bragg grating Fabry-Perot cavity Integer multiple), which can effectively compensate for the optical path difference of the coherent light in the fiber Bragg grating Fabry-Perot cavity, thereby obtaining interference fringes with a larger free spectral range, achieving higher sensitivity, thereby improving
  • the accuracy of fiber Bragg grating Fabry-Perot cavity sensing measurement is introduced.
  • FIG. 1 is a schematic structural diagram of a sensor device based on a fiber Bragg grating Fabry-Perot cavity according to an embodiment of the present invention.
  • This embodiment provides a sensing device based on a fiber Bragg grating Fabry-Perot cavity.
  • the sensing device includes a light source unit 1, an optical fiber circulator 2, an optical fiber sensing unit 3 and Spectrum detection unit 4.
  • the light source unit 1 includes an active mode-locked laser 11, a fiber isolator 12, and a linear polarizer 13.
  • the fiber circulator 2 includes a first port 21, a second port 22, and a third port 23.
  • the fiber sensing unit 3 is a fiber Bragg grating Fabry-Perot cavity, and the spectrum detection unit 4 is a spectrometer.
  • the laser light output by the active mode-locked laser 11 passes through the fiber isolator 12 and the linear polarizer 13 in sequence and then is input to the first port 21 of the fiber circulator 2, and then from the fiber circulator 2
  • the second port 22 is input to the fiber Bragg grating Fabry-Perot cavity, and the laser forms multi-beam interference light after the fiber Fabry-Perot cavity oscillates, and the reflected light from the second port 22
  • the spectral detection unit 4 analyzes and demodulates the interference fringes to obtain the characteristic wavelength drift amount, thereby calculating and acquiring the corresponding detected physical quantity parameter.
  • the active mode-locked fiber laser 11, the fiber isolator 12, the linear polarizer 13, the fiber circulator 3, and the fiber Bragg grating Fabry-Perot cavity (fiber sensing unit 3) are all single-mode fiber devices .
  • the optical fiber sensing unit 3 includes a first high inverse Bragg grating 31 and a second high inverse Bragg grating 32 written into the optical fiber, and the first high inverse Bragg grating 31 and the The second high inverse Bragg gratings 32 have the same structural parameters and are spaced apart from each other to constitute the fiber Bragg grating Fabry-Perot cavity, the first high inverse Bragg grating 31 and the second high inverse Bragg grating 32 The effective distance is the cavity length of the fiber Bragg grating Fabry-Perot cavity.
  • the reflection bandwidth ⁇ of the first high inverse Bragg grating 31 and the second high inverse Bragg grating 32 is more than 0.2 nm, and the reflectance is respectively more than 60%.
  • the first high inverse Bragg grating 31 and the second high inverse Bragg grating 32 are respectively configured as Bragg gratings with a reflectivity of 90% or more.
  • the laser pulse period of the active mode-locked fiber laser 11 is set to be close to i times (i is a positive integer) the oscillation period of the fiber Bragg grating Fabry-Perot cavity, or
  • the equivalent optical path n 1 L 1 of the active mode-locked laser 11 is set to be close to i times the equivalent optical path difference 2n 2 L 2 of the fiber Bragg grating Fabry-Perot cavity, specifically set as : i is a positive integer,
  • n 1 is the equivalent refractive index of the laser cavity of the active mode-locked laser 11
  • L 1 is the equivalent cavity length of the laser cavity of the active mode-locked laser 11
  • n 2 is the fiber Bragg grating method
  • L 2 is the equivalent cavity length of the fiber Bragg grating Fabry-Perot cavity (fiber sensing unit 3)
  • ⁇ is the The reflection center wavelength of the fiber Bragg grating in the
  • the active mode-locked laser 11 is selected as an active mode-locked fiber laser.
  • the refractive indexes n 1 and n 2 can be regarded as equal.
  • the laser pulse period of the active mode-locked laser 11 is set to be close to i times the oscillation period of the FBG-FP cavity, when the difference in the number of oscillations of two adjacent output laser pulses in the FBG-FP cavity is i, the two A pulse will overlap in time, that is, A pq and A (p-1)(q+i) overlap, and interfere.
  • the different pulses output by the active mode-locked laser 11 are coherent.
  • the initial optical path difference corresponding to the time difference between two adjacent laser pulses is n 1 L 1.
  • the Bragg grating fiber Fabry-Perot cavity-based sensing device provided in the above embodiment will eventually form a reflection spectrum in the reflection band of the fiber sensing unit 3 (FBG-FP cavity) Interference fringes, there are periodic notch valleys in the fringes, and the free spectral range (Free Spectral Range, FSR) of the interference fringes is
  • FSR of the existing FBG-FP cavity is
  • the sensing device of the embodiment of the present invention can obtain interference fringes in a larger free spectral range (FSR). And because the "wavelength/phase" sensitivity is proportional to the FSR, the sensor device of the embodiment of the present invention has higher sensitivity.
  • the multiple reflections of the FBG-FP cavity increase the amount of phase modulation by a factor of i, so the final system sensitivity improvement factor is By improving the system sensitivity, the measurement accuracy of the system can be improved. Therefore, in the case where the resolution of the existing demodulation device is limited, the sensing device of the embodiment of the present invention improves the accuracy of the sensing measurement by increasing the sensitivity of the system .
  • the value range of k is:
  • the value range of i is: 1 ⁇ i ⁇ 5.
  • n 2 and L 2 of the fiber Bragg grating Fabry-Perot cavity are selected by control so that:
  • the sensor device based on the fiber Bragg grating Fabry-Perot cavity uses an active mode-locked laser as the signal light source, and controls the pulse period of the light source to be close to the fiber Bragg grating
  • the integer multiple of the oscillation period of the Fabry-Perot cavity (or the equivalent optical path n 1 L 1 of the active mode-locked laser is set to be close to the equivalent optical path of the fiber Bragg grating Fabry-Perot cavity
  • the difference is an integer multiple of 2n 2 L 2 ), which can effectively compensate for the optical path difference of the coherent light in the fiber Fabry-Perot cavity, obtain interference fringes with a larger free spectral range, and achieve higher sensitivity. Thereby improving the accuracy of sensory measurement.

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Abstract

一种基于光纤布拉格光栅法布里-泊罗腔的传感装置，包括光源单元（1）、光纤环形器（2）、光纤传感单元（3）和光谱检测单元（4），光源单元（1）、光纤传感单元（3）和光谱检测单元（4）分别连接至光纤环形器（2），光源单元（1）包括主动锁模激光器（11），光纤传感单元（3）为光纤布拉格光栅法布里-泊罗腔，主动锁模激光器（11）的等效光程为n 1L 1，光纤布拉格光栅法布里-泊罗腔的等效光程差为2n 2L 2；其中，式(aa)，i为正整数，式(bb)。该装置可以有效地补偿光纤布拉格光栅法布里-泊罗腔中的相干光的光程差，获得更大自由光谱范围的干涉条纹，实现了更高的灵敏度，从而提高了传感测量的精度。

Description

基于光纤布拉格光栅法布里-泊罗腔的传感装置 技术领域
本发明涉及传感技术领域，具体是一种基于光纤布拉格光栅法布里-泊罗腔的传感装置。
背景技术
在工业领域的众多行业中，光纤传感器由于其本质安全特性，特别适合于易燃、易爆、强电磁场场所的传感应用要求，可以方便、准确和有效地对各种环境尤其是各种恶劣环境中有关物理量的检测。
光纤布拉格光栅(Fiber Bragg Grating，FBG)传感器的中心峰值波长通常与其所受的温度和应变相关，因此根据此原理，可以将光纤光栅制作成光纤光栅温度传感器和光纤光栅应变传感器。目前，为了弥补FBG传感器峰值波长不能准确测量的缺点，在FBG传感器的基础上发展出了光纤布拉格光栅法布里-泊罗腔(FBG-FP)传感器。
光纤布拉格光栅法布里-泊罗腔是在光纤纤芯中相隔一定距离的两处写入两个参数相同的布拉格光栅，当满足光栅反射条件的某个特定波长的光信号入射时，会被耦合成反射与透射光波，从而使得光波在两光栅之间振荡，形成多光束干涉，从而在布拉格光栅反射带内形成高精细度干涉条纹。利用光纤布拉格光栅法布里-泊罗腔进行物理量感知的基本原理是：温度、应变等物理量的变化会引起两光栅之间所构成的法布里-泊罗腔的腔长变化，导致干涉条纹的特征波长(透射峰波长或反射峰波长)发生漂移，由于透射峰和反射峰的3dB带宽很小，因此，可以准确测量很小的波长漂移，其灵敏度与FBG传感器相当，但是可以提高测量精度。
虽然目前的FBG-FP传感器相比于FBG传感器提高了波长解调精度，然而，其提高的空间也受限于解调设备的分辨率，在光谱仪的解调方式下可达10pm，在扫描式光源解调下，也只能达到1pm，对应的应变灵敏度为微应变量 级，温度灵敏度为0.1摄氏度，不能满足更高的需求，例如，地球潮汐的测量，地震前兆观测等。因此，如何进一步提高FBG-FP传感器的传感测量的精度是业内一直在探索解决的问题。
发明内容
有鉴于此，本发明提供了一种基于光纤布拉格光栅法布里-泊罗腔的传感装置，该装置可以获得更大自由光谱范围的干涉条纹，实现了更高的灵敏度，从而提高了传感测量的精度。
为了达到上述发明目的，本发明采用了如下的技术方案：
一种基于光纤布拉格光栅法布里-泊罗腔的传感装置，包括光源单元、光纤环形器、光纤传感单元和光谱检测单元，所述光源单元连接至所述光纤环形器的第一端口，所述光纤传感单元连接至所述光纤环形器的第二端口，所述光谱检测单元连接至所述光纤环形器的第三端口，其中，所述光源单元包括主动锁模激光器，所述光纤传感单元为光纤布拉格光栅法布里-泊罗腔，所述主动锁模激光器的等效光程为n 1L 1，所述光纤布拉格光栅法布里-泊罗腔的等效光程差为2n 2L 2；其中，
Figure PCTCN2019124598-appb-000001
i为正整数，
Figure PCTCN2019124598-appb-000002
其中，n 1为所述主动锁模激光器的激光腔的等效折射率，L 1为所述主动锁模激光器的激光腔的等效腔长，n 2为所述光纤布拉格光栅法布里-泊罗腔的等效折射率，L 2为所述光纤布拉格光栅法布里-泊罗腔的等效腔长，λ为所述光纤布拉格光栅法布里-泊罗腔中光纤布拉格光栅的反射中心波长，Δλ为所述光纤布拉格光栅法布里-泊罗腔中光纤布拉格光栅的反射带宽。
优选地，所述k的取值范围是：
Figure PCTCN2019124598-appb-000003
优选地，所述i的取值范围是：1≤i≤5。
优选地，所述光纤布拉格光栅法布里-泊罗腔的等效折射率n 2和等效腔长L 2满足条件：
Figure PCTCN2019124598-appb-000004
具体地，所述光纤传感单元包括写入到光纤中的第一高反布拉格光栅和第 二高反布拉格光栅，所述第一高反布拉格光栅和所述第二高反布拉格光栅具有相同的结构参数并且相互间隔设置构成所述光纤布拉格光栅法布里-泊罗腔。
具体地，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射带宽Δλ为0.2nm以上，反射率分别为60％以上。
具体地，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射率分别为90％以上。
具体地，所述主动锁模激光器为主动锁模光纤激光器。
具体地，所述光源单元还包括光纤隔离器和线偏器，所述主动锁模激光器输出的激光依次通过所述光纤隔离器和所述线偏器后输入到所述光纤环形器的第一端口。
具体地，所述主动锁模光纤激光器、光纤隔离器、线偏器、光纤环形器以及光纤布拉格光栅法布里-泊罗腔均为单模光纤器件。
本发明实施例提供的基于光纤布拉格光栅法布里-泊罗腔的传感装置，采用主动锁模激光器作为信号光源，通过将主动锁模激光器的等效光程n 1L 1设置为接近于光纤布拉格光栅法布里-泊罗腔的等效光程差2n 2L 2的整数倍(或者说是控制激光器的激光脉冲周期为接近于光纤布拉格光栅法布里-泊罗腔的振荡周期的整数倍)，由此可以有效地补偿光纤布拉格光栅法布里-泊罗腔中的相干光的光程差，由此获得更大自由光谱范围的干涉条纹，实现了更高的灵敏度，从而提高了光纤布拉格光栅法布里-泊罗腔传感测量的精度。
附图说明
图1是本发明实施例的基于光纤布拉格光栅法布里-泊罗腔的传感装置的结构示意图。
具体实施方式
以下，将参照附图来详细描述本发明的实施例。然而，可以以许多不同的形式来实施本发明，并且本发明不应该被解释为限制于这里阐述的具体实施例。相反，提供这些实施例是为了解释本发明的原理及其实际应用，从而使本领域的其他技术人员能够理解本发明的各种实施例和适合于特定预期应用的 各种修改。
本实施例提供了一种基于光纤布拉格光栅法布里-泊罗腔的传感装置，如图1所示，所述传感装置包括光源单元1、光纤环形器2、光纤传感单元3和光谱检测单元4。
本实施例中，所述光源单元1包括主动锁模激光器11、光纤隔离器12和线偏器13，所述光纤环形器2包括第一端口21、第二端口22和第三端口23，所述光纤传感单元3为光纤布拉格光栅法布里-泊罗腔，所述光谱检测单元4为光谱仪。
其中，所述主动锁模激光器11输出的激光依次通过所述光纤隔离器12和所述线偏器13后输入到所述光纤环形器2的第一端口21，再从所述光纤环形器2的第二端口22输入至所述光纤布拉格光栅法布里-泊罗腔，激光在所述光纤法布里-泊罗腔振荡后形成多光束干涉光，其中的反射光从所述第二端口22返回至所述光纤环形器2，再从所述光纤环形器2的第三端口23输入至所述光谱检测单元4，由所述光谱检测单元4对反射光的光谱进行解调。其中，当所述光纤法布里-泊罗腔所探测的温度、应变等物理量的变化时，会引起光纤布拉格光栅法布里-泊罗腔的等效光程差发生变化，导致干涉条纹的特征波长发生漂移，通过所述光谱检测单元4对干涉条纹进行分析解调获得特征波长漂移量，从而计算获得相应的所探测的物理量参数。
具体地，所述主动锁模光纤激光器11、光纤隔离器12、线偏器13、光纤环形器3以及光纤布拉格光栅法布里-泊罗腔(光纤传感单元3)均为单模光纤器件。
其中，如图1所示，所述光纤传感单元3包括写入到光纤中的第一高反布拉格光栅31和第二高反布拉格光栅32，所述第一高反布拉格光栅31和所述第二高反布拉格光栅32具有相同的结构参数并且相互间隔设置构成所述光纤布拉格光栅法布里-泊罗腔，所述第一高反布拉格光栅31和所述第二高反布拉格光栅32的有效间距即为所述光纤布拉格光栅法布里-泊罗腔的腔长。
具体地，所述第一高反布拉格光栅31和所述第二高反布拉格光栅32的反射带宽Δλ为0.2nm以上，反射率分别为60％以上。在更为优选的方案中，所述第一高反布拉格光栅31和所述第二高反布拉格光栅32分别设置为反射率为 90％以上的布拉格光栅。
本发明实施例中，所述主动锁模光纤激光器11的激光脉冲周期设置为接近于所述光纤布拉格光栅法布里-泊罗腔的振荡周期的i倍(i为正整数)，或者说是将所述主动锁模激光器11的等效光程n 1L 1设置为接近于所述光纤布拉格光栅法布里-泊罗腔的等效光程差2n 2L 2的i倍，具体设置为：
Figure PCTCN2019124598-appb-000005
i为正整数，
Figure PCTCN2019124598-appb-000006
其中，n 1为所述主动锁模激光器11的激光腔的等效折射率，L 1为所述主动锁模激光器11的激光腔的等效腔长，n 2为所述光纤布拉格光栅法布里-泊罗腔(光纤传感单元3)的等效折射率，L 2为所述光纤布拉格光栅法布里-泊罗腔(光纤传感单元3)的等效腔长，λ为所述光纤布拉格光栅法布里-泊罗腔中光纤布拉格光栅的反射中心波长，Δλ为所述光纤布拉格光栅法布里-泊罗腔中光纤布拉格光栅的反射带宽。
在本实施例中，所述主动锁模激光器11选择为主动锁模光纤激光器，此时折射率n 1和n 2可以看做是相等的，通过控制腔长L 1为接近于腔长L 2的偶数倍，即可使得所述主动锁模激光器11的激光脉冲周期为接近于所述光纤布拉格光栅法布里-泊罗腔的振荡周期的整数倍。
如上实施例提供的基于布拉格光栅光纤法布里-泊罗腔的传感装置，主动锁模激光器11输出的脉冲光A p(p＝1，2，3…)在光纤传感单元3(FBG-FP腔)反射可形成脉冲序列A pq(p＝1，2，3…；q＝1，2，3…)，q代表在FBG-FP腔内振荡次数。而由于所述主动锁模激光器11的激光脉冲周期设置为接近于FBG-FP腔的振荡周期的i倍，当相邻两个输出激光脉冲在FBG-FP腔内振荡次数差异为i时，两个脉冲会发生时间上的重叠，即A pq与A (p-1)(q+i)重叠，并进行干涉。主动锁模激光器11输出的不同的脉冲是相干的，相邻两个激光脉冲时间差对应的初始光程差为n 1L 1，这两个脉冲在FBG-FP腔内振荡次数差为i时，产生的附加光程差为-2i n 2L 2，最终相邻两个脉冲的光程差OPD可以表示为：OPD＝n 1L 1-2i n 2L 2。同理，相隔j个周期的两个脉冲，在腔内振荡次数差异为j×i(j＝1，2，3…)时会发生时间上的重叠，即A pq与A (p-j)(q+j×i)重叠，并进行干涉，两个脉冲的光程差OPD可以表示为：OPD＝j(n 1L 1-2i n 2L 2)。因此，主动锁模激光器11输出的脉冲光在光纤传感单元3反射的脉冲序列可形成多光束干涉。
根据多光束干涉理论可以得知，如上实施例提供的基于布拉格光栅光纤法 布里-泊罗腔的传感装置，最终在光纤传感单元3(FBG-FP腔)反射带内形成反射谱的干涉条纹，条纹中有周期性的陷波谷，且该干涉条纹的自由光谱范围(Free Spectral Range，FSR)为
Figure PCTCN2019124598-appb-000007
而现有的FBG-FP腔的FSR为
Figure PCTCN2019124598-appb-000008
根据：
Figure PCTCN2019124598-appb-000009
i为正整数，
Figure PCTCN2019124598-appb-000010
则|n 1L 1-2in 2L 2|＝2in 2L 2·|k|＜2n 2L 2。因此本发明实施例的传感装置可以获得更大自由光谱范围(FSR)的干涉条纹。而由于“波长/相位”灵敏度与FSR成正比，因此，本发明实施例的传感装置具有更高的灵敏度。另外，FBG-FP腔的多次反射使相位调制量提高i倍，因此最终的系统灵敏度提高的倍数为
Figure PCTCN2019124598-appb-000011
通过提高系统灵敏度可以提高系统的测量精度，因此，在现有的解调设备的分辨率受限的情况下，本发明实施例的传感装置通过提高系统的灵敏度从而提高了传感测量的精度。
在优选的方案中，所述k的取值范围是：
Figure PCTCN2019124598-appb-000012
在优选的方案中，所述i的取值范围是：1≤i≤5。
在优选的方案中，通过控制选择所述光纤布拉格光栅法布里-泊罗腔的参数n 2和L 2使得：
Figure PCTCN2019124598-appb-000013
综上所述，根据本发明的实施例提供的基于光纤布拉格光栅法布里-泊罗腔的传感装置，采用主动锁模激光器作为信号光源，并且控制光源的脉冲周期为接近于光纤布拉格光栅法布里-泊罗腔的振荡周期的整数倍(或者说是将主动锁模激光器的等效光程n 1L 1设置为接近于光纤布拉格光栅法布里-泊罗腔的等效光程差2n 2L 2的整数倍)，由此可以有效地补偿光纤法布里-泊罗腔中的相干光的光程差，获得更大自由光谱范围的干涉条纹，实现了更高的灵敏度，从而提高了传感测量的精度。
虽然已经参照特定实施例示出并描述了本发明，但是本领域的技术人员将理解：在不脱离由权利要求及其等同物限定的本发明的精神和范围的情况下，可在此进行形式和细节上的各种变化。

Claims (20)

  1. 一种基于光纤布拉格光栅法布里-泊罗腔的传感装置，包括光源单元、光纤环形器、光纤传感单元和光谱检测单元，所述光源单元连接至所述光纤环形器的第一端口，所述光纤传感单元连接至所述光纤环形器的第二端口，所述光谱检测单元连接至所述光纤环形器的第三端口，其中，所述光源单元包括主动锁模激光器，所述光纤传感单元为光纤布拉格光栅法布里-泊罗腔，所述主动锁模激光器的等效光程为n 1L 1，所述光纤布拉格光栅法布里-泊罗腔的等效光程差为2n 2L 2；其中，
    Figure PCTCN2019124598-appb-100001
    i为正整数，
    Figure PCTCN2019124598-appb-100002
    其中，n 1为所述主动锁模激光器的激光腔的等效折射率，L 1为所述主动锁模激光器的激光腔的等效腔长，n 2为所述光纤布拉格光栅法布里-泊罗腔的等效折射率，L 2为所述光纤布拉格光栅法布里-泊罗腔的等效腔长，λ为所述光纤布拉格光栅法布里-泊罗腔中光纤布拉格光栅的反射中心波长，Δλ为所述光纤布拉格光栅法布里-泊罗腔中光纤布拉格光栅的反射带宽。
  2. 根据权利要求1所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述k的取值范围是：
    Figure PCTCN2019124598-appb-100003
  3. 根据权利要求1所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述i的取值范围是：1≤i≤5。
  4. 根据权利要求1所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光纤布拉格光栅法布里-泊罗腔的等效折射率n 2和等效腔长L 2满足条件：
    Figure PCTCN2019124598-appb-100004
  5. 根据权利要求1所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光纤传感单元包括写入到光纤中的第一高反布拉格光栅和第二高反布拉格光栅，所述第一高反布拉格光栅和所述第二高反布拉格光栅具有相同的结构参数并且相互间隔设置构成所述光纤布拉格光栅法布里-泊罗腔。
  6. 根据权利要求2所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光纤传感单元包括写入到光纤中的第一高反布拉格光栅和第二高反 布拉格光栅，所述第一高反布拉格光栅和所述第二高反布拉格光栅具有相同的结构参数并且相互间隔设置构成所述光纤布拉格光栅法布里-泊罗腔。
  7. 根据权利要求4所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光纤传感单元包括写入到光纤中的第一高反布拉格光栅和第二高反布拉格光栅，所述第一高反布拉格光栅和所述第二高反布拉格光栅具有相同的结构参数并且相互间隔设置构成所述光纤布拉格光栅法布里-泊罗腔。
  8. 根据权利要求5所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射带宽Δλ为0.2nm以上，反射率分别为60％以上。
  9. 根据权利要求6所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射带宽Δλ为0.2nm以上，反射率分别为60％以上。
  10. 根据权利要求7所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射带宽Δλ为0.2nm以上，反射率分别为60％以上。
  11. 根据权利要求8所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射率分别为90％以上。
  12. 根据权利要求9所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射率分别为90％以上。
  13. 根据权利要求10所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述第一高反布拉格光栅和所述第二高反布拉格光栅的反射率分别为90％以上。
  14. 根据权利要求1所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述主动锁模激光器为主动锁模光纤激光器。
  15. 根据权利要求2所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述主动锁模激光器为主动锁模光纤激光器。
  16. 根据权利要求4所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述主动锁模激光器为主动锁模光纤激光器。
  17. 根据权利要求14所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光源单元还包括光纤隔离器和线偏器，所述主动锁模激光器输出的激光依次通过所述光纤隔离器和所述线偏器后输入到所述光纤环形器的第一端口。
  18. 根据权利要求15所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光源单元还包括光纤隔离器和线偏器，所述主动锁模激光器输出的激光依次通过所述光纤隔离器和所述线偏器后输入到所述光纤环形器的第一端口。
  19. 根据权利要求16所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述光源单元还包括光纤隔离器和线偏器，所述主动锁模激光器输出的激光依次通过所述光纤隔离器和所述线偏器后输入到所述光纤环形器的第一端口。
  20. 根据权利要求17所述的基于光纤布拉格光栅法布里-泊罗腔的传感装置，其中，所述主动锁模光纤激光器、光纤隔离器、线偏器、光纤环形器以及光纤布拉格光栅法布里-泊罗腔均为单模光纤器件。
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