WO2021196815A1 - 基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置及方法 - Google Patents

基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置及方法 Download PDF

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WO2021196815A1
WO2021196815A1 PCT/CN2021/070284 CN2021070284W WO2021196815A1 WO 2021196815 A1 WO2021196815 A1 WO 2021196815A1 CN 2021070284 W CN2021070284 W CN 2021070284W WO 2021196815 A1 WO2021196815 A1 WO 2021196815A1
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chirped
grating
fiber
chirped grating
measurement area
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PCT/CN2021/070284
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English (en)
French (fr)
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李政颖
王洪海
王立新
桂鑫
郭会勇
姜德生
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武汉理工大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
    • G01V1/18—Receiving elements, e.g. seismometer, geophone or torque detectors, for localised single point measurements
    • G01V1/186—Hydrophones
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/22—Transmitting seismic signals to recording or processing apparatus
    • G01V1/226—Optoseismic systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/0208—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
    • G02B6/02085—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the grating profile, e.g. chirped, apodised, tilted, helical
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/0208—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
    • G02B6/02085—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the grating profile, e.g. chirped, apodised, tilted, helical
    • G02B2006/0209—Helical, chiral gratings

Definitions

  • the invention relates to the technical field of optical fiber sensing, in particular to an enhanced hydrophone detection device and method based on a low bending loss chirped grating array optical fiber.
  • Sound waves are the only form of energy known to humans that can be transmitted over long distances in sea water.
  • a hydrophone is a type of sensor that uses sound waves propagating in the ocean as an information carrier to detect underwater targets and realize underwater navigation, measurement, and communication.
  • Piezoelectric hydrophones and interferometric fiber optic hydrophones are currently the most widely used underwater acoustic detectors.
  • piezoelectric hydrophones have outstanding problems such as non-anti-electromagnetic interference, difficult to reuse, large size, low sensitivity, and small dynamic range, which restrict their application.
  • fiber-optic hydrophones Compared with traditional piezoelectric hydrophones, fiber-optic hydrophones have the advantages of high sensitivity, good frequency response, large dynamic range, and anti-electromagnetic interference. It has become an important advanced technology in the field of hydrophones. And with the continuous development of various submarine technologies, higher requirements are put forward on the scale, sensitivity, and volume of hydrophones. The earliest single-point optical fiber structured hydrophones have been unable to meet the needs of large-scale and distributed detection. A distributed sensing system with a large-scale array using the Michelson interference principle, but the large-scale array brings about an increase in optical devices and volume, and a large number of fiber fusion points are generated, which increases the optical path loss and reduces the sensing distance ( References, Rao Wei. Research on key technologies for high-resolution detection of submarine strata structure with fiber-optic vector hydrophone[D]. National University of Defense Technology, 2012.).
  • the FBG-based DFB fiber laser hydrophone is used to detect the underwater acoustic signal by using the change in the output wavelength of the narrow linewidth laser.
  • the sound pressure sensitivity of this structure has been improved, but because the resonant cavity of the DFB laser is very short, the time division multiplexing technology cannot be used to construct an array.
  • the use of wavelength division multiplexing technology can only multiplex dozens of hydrophones, which limits the multiplexing scale and cannot meet the requirements of large-scale hydrophone arrays (Reference Tanaka S, et al. Fiber bragg grating hydrophone array using multi-wavelength laser: simultaneous multipoint underwater acoustic detection [C]//International Conference on Optical Fibre Sensors. International Society for Optics and Photonics, 2009.).
  • the acoustic wave detection using the optical fiber distributed acoustic wave detection (DAS) technology is based on the optical fiber backward Rayleigh scattering effect ⁇ -OTDR technology.
  • the backward Rayleigh scattering used in this method has low coupling efficiency and weak reflectivity, resulting in low signal-to-noise ratio, low sensitivity, and poor response.
  • this method is based on optical fiber as the sensor, and its transmission and sensing are the same optical fiber. It will increase the sensitivity of underwater acoustic signal detection and will cause the transmission loss of optical signal, and further reduce the signal ratio, so it is difficult to detect underwater acoustic waves.
  • the measurement is made for structural sensitization.
  • optical fiber distributed acoustic wave detection (DAS) technology is difficult to meet the requirements of high signal-to-noise ratio and high sensitivity in hydrophones (Reference: Dong Jie. Optical fiber distributed underwater acoustic wave measurement based on spatial differential interference [J]. Optics and Precision Engineering, 2017(9).).
  • the purpose of the present invention is to provide an enhanced hydrophone detection device based on a low bending loss chirped grating array fiber.
  • the present invention can improve the sensor signal strength by writing a reflection grating on the optical fiber, and can improve the sensor through structural enhancement.
  • the sound pressure sensitivity can achieve long-distance multiplexing without solder joints of large-capacity hydrophones, so as to meet more practical needs and application scenarios.
  • the present invention includes an interferometric distributed fiber grating acoustic sensor demodulator, a chirped grating array fiber, and a metal elastic cylinder.
  • the chirped grating array fiber has two adjacent chirped gratings.
  • the optical fiber in between constitutes the grating measurement area.
  • the grating measurement area includes the odd-numbered chirped grating measurement area and the even-numbered chirped grating measurement area.
  • the metal elastic cylinder is arranged in a straight line in the length direction, and all gratings in the chirped grating array fiber are located on the same straight line along the length of the metal elastic cylinder.
  • the optical signal output end of the interferometric distributed fiber grating acoustic sensor demodulator is connected to the chirp One end of the chirped grating array fiber and the other end of the chirped grating array fiber are knotted and suspended or connected to a fiber terminator.
  • the interferometric distributed fiber grating acoustic sensor demodulator uses short pulse matching interferometry to perform independent interference demodulation on the grating measurement area on the chirped grating array fiber, and demodulates the phase change information of each grating measurement area. Then, the phase change information of each grating measurement area is linearly restored to obtain the time frequency information of the external underwater sound pressure felt by each grating measurement area.
  • the present invention uses chirped grating array fiber as the basic underwater sensing unit.
  • the large-capacity identical weakly chirped fiber grating array improves the signal-to-noise ratio of the system by virtue of the stronger reflected light signal intensity than traditional Rayleigh scattered light. 30 ⁇ 40dB.
  • the single large-capacity identical weakly chirped fiber grating array used in the present invention has no fusion splice point, no splice loss, and improves the sensing distance.
  • the metal cylinder of the present invention adopts elastic material, which has high sensitivity and dynamic pressure response characteristics, has a positive and obvious sensitization effect on the optical fiber wound on it, and can control the sensitivity of the wound optical fiber, and at the same time, it also ensures
  • the chirped grating array fiber sensor has the feature of full fiber (no fusion splice).
  • the chirped grating array fiber used in the present invention is prepared on a low-loss bend-insensitive fiber, which increases structural sensitivity while reducing the transmission loss caused by bending, and reduces the impact on the sensing distance.
  • the chirped grating array fiber used in the present invention is written on-line on a low-loss bending insensitive fiber.
  • the type is an identical weakly chirped grating, and its characteristic parameters such as reflection spectrum, reflectivity, and effective bandwidth are basically the same.
  • the chirped grating has a wider spectrum, with a 3dB bandwidth of about 4nm, which better suppresses the influence of spectral temperature drift on underwater acoustic detection; it is not currently used in hydrophones
  • the scheme of using a chirped grating array is written on-line on a low-loss bending insensitive fiber.
  • the present invention uses an interferometric distributed fiber grating acoustic sensor demodulator, and uses short pulse matching interferometry to demodulate the phase change information of each grating measurement area, and then linearly restore the phase change information of each grating measurement area Obtain the time and frequency information of the external underwater sound pressure felt by each grating measurement area, with strong positioning ability, high demodulation sensitivity and accuracy, fast speed, and good real-time performance.
  • Figure 1 is a schematic diagram of the structure of the present invention
  • 1 interferometric distributed fiber grating acoustic sensor demodulator, 2-chirped grating array fiber, 2.1—chirped grating, 2.2—odd-numbered chirped grating measurement area, 2.3—even-numbered chirped grating measurement area, 3 —Metal elastic cylinder.
  • an enhanced hydrophone detection device based on a low bending loss chirped grating array fiber, including an interferometric distributed fiber grating acoustic sensor demodulator 1, a chirped grating array fiber 2 and a metal elastic cylinder 3 ,
  • the optical fiber between two adjacent chirped gratings 2.1 in the chirped grating array fiber 2 constitutes a grating measurement area, and the grating measurement area includes an odd-numbered chirped grating measurement area 2.2 and an even-numbered chirped grating measurement area 2.3.
  • the chirped grating measurement area 2.2 is used as a sensitive area and is tightly wound on the metal elastic cylinder 3 (increasing the sensor length and density per unit area to increase the sensor’s sensing sensitivity).
  • the even-numbered chirped grating measurement area 2.3 is to meet the requirements of hydrophones.
  • the metal elastic cylinder 3 is preferably a hollow stainless steel cylinder, which has good chemical stability and dynamic pressure response characteristics.
  • the interferometric distributed fiber grating acoustic sensor demodulator 1 uses short pulse matching interferometry (specifically, the 3 ⁇ 3 coupler phase demodulation method in short pulse matching interferometry, and the demodulation frequency is 10kHz) Perform independent interference demodulation on the grating measurement area on the chirped grating array fiber 2, and demodulate the phase change information of each grating measurement area (reference Zhengying, Li, et al. "Simultaneous distributed static and dynamic sensing based on ultra-short fiber Bragg gratings.
  • the chirped grating array fiber 2 is a low-bending loss chirped grating array fiber, and the low-bending loss chirped grating array fiber is formed by inscribed on-line on a low-loss bend-insensitive single-mode fiber with low bending loss.
  • a single large-capacity (more than 1,000 gratings) in the chirped grating array fiber is identical and weak.
  • the chirped fiber grating array has no fusion splices (no fusion splices guarantees low loss), and the type of chirped grating 2.1 is identical and weak.
  • Reflectivity chirped grating the reflectivity of the identical weak reflectivity chirped grating is less than -30dB, and the 10 turns of the chirped grating array fiber with low bending loss has a 15mm macrobending additional loss ⁇ 0.2dB.
  • the wider reflection bandwidth of the identical weakly chirped grating can suppress the influence of external temperature changes on the demodulation optical system.
  • the grating lengths of the identical weakly-chirped gratings are all equal, and the grating intervals of two adjacent identically weakly-chirped gratings are all equal.
  • This equidistant (within a certain error range) is an identical weakly-chirped grating array. It is conducive to the accurate positioning and detection of underwater targets.
  • compared with the traditional ⁇ -OTDR technology based on the Rayleigh scattering effect it can ensure a higher signal-to-noise ratio of the system.
  • the chirped grating has a wider spectrum than other ordinary gratings (such as temperature sensitive gratings), and the 3dB bandwidth of the grating reflection spectrum of the identical weakly chirped grating is 1 ⁇ 6nm, which can better suppress the spectral temperature drift. Impact on underwater acoustic detection.
  • the identical weakly chirped gratings in the chirped grating array optical fiber 2 are distributed at equal intervals, and the chirped grating array exhibits the identity of the parameter index, that is, the reflection spectra of all the chirped gratings on the optical fiber,
  • the characteristic parameters such as reflectance and effective bandwidth are consistent, so that the demodulation optical system is more convenient in the adjustment of optical parameters such as optical pulse width and pulse intensity, while ensuring the reliability and stability of the demodulation optical system.
  • the axial length of the odd-numbered chirped grating measurement zone 2.2 wound around the optical fiber is much smaller than the length of the even-numbered chirped grating measurement zone 2.3, which improves the enhancement effect of the enhanced sensitivity zone on underwater sound and at the same time ensures the hydrophone The need for long-distance distributed detection of the device.
  • the winding density and tightness of the wound optical fiber can be adjusted by reserving a certain length of optical fiber, so that the detection sensitivity of the hydrophone can be adjusted within a certain range according to the winding method (tension, density).
  • the low-bending loss chirped grating array fiber based on the low-loss bending-insensitive single-mode fiber adopts a method of winding an elastic body for structural sensitization, and the loss caused by bending has little effect on the transmission distance.
  • the deformation of the metal elastic cylinder 3 caused by underwater sound is directly converted into the axial strain of the chirped grating array fiber 2 wound on it.
  • the interference type distribution is used.
  • the optical fiber grating acoustic sensor demodulator 1 demodulates the phase change information caused by underwater sound in real time, so as to realize high-sensitivity sound pressure signal detection. It uses the axial strain of the optical fiber, that is, the change in the length of the optical fiber to realize underwater sound detection. Below 10kHz) has a good dynamic response capability.
  • a sound pressure detection method based on low bending loss chirped grating array fiber which is characterized in that it includes the following steps:
  • Step 1 Connect one end of the chirped grating array fiber 2 to the optical signal output end of the interferometric distributed fiber grating acoustic sensor demodulator 1, and the other end of the chirped grating array fiber 2 is knotted and suspended or connected to a fiber terminator;
  • Step 2 The chirped grating array fiber 2 is wound and extended along the metal elastic cylinder 3.
  • the rule of winding and extension is that the optical fiber between two adjacent chirped gratings 2.1 in the chirped grating array fiber 2 constitutes the grating measurement area, of which, odd number
  • the chirped grating measurement area 2.2 is used as a sensitive area and is tightly wound on the metal elastic cylinder 3.
  • the even-numbered chirped grating measurement area 2.3 is arranged linearly along the length of the metal elastic cylinder 3 in order to meet the needs of the distributed drag of the hydrophone, and All chirped gratings 2.1 in the chirped grating array optical fiber 2 are located on the same straight line along the length of the metal elastic cylinder 3;
  • Step 3 The deformation of the metal elastic cylinder 3 under the action of underwater sound is directly converted into the axial strain of the chirped grating array fiber 2 wound on it. According to the phase stress and strain model of the fiber, the interferometric distributed fiber is used The grating acoustic sensor demodulator 1 demodulates the phase change information caused by underwater sound in real time, thereby realizing high-sensitivity sound pressure signal detection.
  • step 3 of the above technical solution according to the phase stress and strain model of the optical fiber, the interferometric distributed fiber grating acoustic sensor demodulator 1 is used to demodulate the phase change information caused by underwater sound in real time, so as to realize the sound pressure signal detection.
  • the specific method is:
  • the interferometric distributed fiber grating acoustic sensor demodulator 1 uses short pulse matching interferometry to perform independent interference demodulation on the grating measurement area on the chirped grating array fiber 2 and demodulates the phase change of each grating measurement area. The information is then linearly restored through the phase change information of each grating measurement area to obtain the time frequency information of the external underwater sound pressure felt by each grating measurement area.
  • the invention uses the dynamic pressure response characteristics of the metal elastic cylindrical material itself to solve the defect that the optical fiber itself is not sensitive to underwater sound pressure in the existing optical fiber hydrophone.
  • the acoustic sensing demodulation system greatly improves the sensitivity of acoustic sensing (in the case of a minor impact on the detection length, the winding of the (odd area) at the same length increases the response length of the optical fiber and increases the sensitivity).

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Abstract

一种基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，包括干涉型分布式光纤光栅声学传感解调仪（1）、低弯曲损耗啁啾光栅阵列光纤（2）和金属弹性圆筒（3）；低弯曲损耗啁啾光栅阵列光纤（2）基于低损耗弯曲不敏感单模光纤在线制备而成，低弯曲损耗啁啾光栅阵列光纤（2）中相邻两个啁啾光栅（2.1）之间的光纤构成光栅测区，光栅测区包括奇数啁啾光栅测区（2.2）和偶数啁啾光栅测区（2.3），其中，奇数啁啾光栅测区（2.2）缠绕在金属弹性圆筒（3）上，偶数啁啾光栅测区（2.3）沿金属弹性圆筒（3）长度方向直线布设；干涉型分布式光纤光栅声学传感解调仪（1）的光学信号输出端连接低弯曲损耗啁啾光栅阵列光纤（2）的一端；低弯曲损耗啁啾光栅阵列光纤（2）的另一端打结悬空或者连接光纤终结器。还包括一种基于低弯曲损耗啁啾光栅阵列光纤的声压检测方法。

Description

基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置及方法 技术领域
本发明涉及光纤传感技术领域，具体地指一种基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置及方法。
背景技术
声波是人类已知的唯一能在海水中远距离传输的能量形式。水听器是利用在海洋中传播的声波作为信息载体对水下目标进行探测以及实现水下导航、测量和通信的一类传感器。
压电式水听器和干涉式光纤水听器是目前应用最广泛的水声探测器件。压电式水听器发展较早，技术更加成熟，结构和制作工艺更简单，大规模生产时一致性可以得到相对较好的控制。但是，压电式水听器存在不抗电磁干扰、不易复用、体积大、灵敏度低、动态范围小等突出问题，使得其应用受到一定限制。
光纤水听器与传统的压电水听器相比，具有灵敏度高、频响特性好、动态范围大、抗电磁干扰等优点，已经成为水听器领域中一种重要的先进技术。并且随着各种潜艇技术的不断发展，对水听器规模、水听检测灵敏度、体积都提出了更高的要求。最早出现的单点式光纤结构式水听器已难以满足大规模及分布式检测的需求。采用Michelson干涉原理的具有较大规模阵列的分布式传感系统，但大规模阵列带来的光学器件以及体积的增加，并产生大量的光纤熔接点，增加光路损耗的同时降低了传感距离(参考文献，饶伟.光纤矢量水听器海底地层结构高分辨率探测关键技术研究[D].国防科学技术大学,2012.)。
基于光纤布拉格光栅(Fiber Bragg Gratings,FBG)的波长调制型水听器，其传感基元不包含额外的光学器件，可实现水听器阵列， 但其波长调制原理决定了声压灵敏度较低，而且多个传感器串联需要熔融焊接，无法实现大规模的传感阵列，难以满足实际应用(参考文献Takahashi N,et al.Underwater Acoustic Sensor with Fiber Bragg Grating[J].Optical Review,1997,4(6):691-694.)。
采用基于FBG的DFB光纤激光器型水听器，利用窄线宽激光输出波长的变化检测水声信号。该结构的声压灵敏度获得了提高，但由于DFB激光器的谐振腔很短，不能采用时分复用技术构建阵列。而由于光纤焊接点的光损耗问题，采用波分复用技术也仅能复用数十个水听器，限制了其复用规模，无法满足大规模水听阵列的要求(参考文献Tanaka S，et al.Fiber bragg grating hydrophone array using multi-wavelength laser:simultaneous multipoint underwater acoustic detection[C]//International Conference on Optical Fibre Sensors.International Society for Optics and Photonics,2009.)。
采用光纤分布式声波检测(DAS)技术的声波检测，传统方法是基于光纤后向瑞利散射效应的Φ-OTDR技术。但是该方法采用的后向瑞利散射的耦合效率不高、反射率弱，导致信噪比不高、灵敏度低、响应差。而且，该方法基于光纤作为传感器，其传输与传感为同一根光纤，在对水声信号探测增敏的同时会导致光信号的传输损耗，进一步的降低信号比，因此难以对水下声波的测量进行结构上的增敏。综上所述，光纤分布式声波检测(DAS)技术难以满足水听器中高信噪比、高灵敏度的要求(参考文献：董杰.空间差分干涉的光纤分布式水下声波测量[J].光学精密工程,2017(9).)。
上述方法很难同时实现在结构可增敏、阵列规模大、检测距离长、线性细的分布式水听检测需求。基于以上问题，需要寻找一种传感信号强、结构可增敏、能够大容量长距离多点复用的新型分布式光纤水听检测技术。
发明内容
本发明的目的就是要提供一种基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，本发明能够通过在光纤上刻写反射光 栅提高传感信号强度、能够通过结构增敏提高传感器的声压灵敏度、能够实现大容量的水听器的无焊点长距离复用，从而满足更多的实际需要和应用场景。
为实现此目的，本发明所设计的包括干涉型分布式光纤光栅声学传感解调仪、啁啾光栅阵列光纤和金属弹性圆筒，所述啁啾光栅阵列光纤中相邻两个啁啾光栅之间的光纤构成光栅测区，光栅测区包括奇数啁啾光栅测区和偶数啁啾光栅测区，其中，奇数啁啾光栅测区缠绕在金属弹性圆筒上，偶数啁啾光栅测区沿金属弹性圆筒长度方向直线布设，且啁啾光栅阵列光纤中的所有光栅位于沿金属弹性圆筒长度方向同一直线上，干涉型分布式光纤光栅声学传感解调仪的光学信号输出端连接啁啾光栅阵列光纤的一端，啁啾光栅阵列光纤的另一端打结悬空或者连接光纤终结器。
所述干涉型分布式光纤光栅声学传感解调仪利用短脉冲匹配干涉法对啁啾光栅阵列光纤上的光栅测区进行独立干涉解调，解调得到每个光栅测区的相位变化信息，再通过每个光栅测区的相位变化信息线性还原得到每个光栅测区所感受的外界的水声声压的时间频率信息。
本发明的有益效果：
1、本发明采用啁啾光栅阵列光纤作为水下基本传感单元，大容量全同弱啁啾光纤光栅阵列凭借比传统瑞利散射光较强的反射光信号强度使得系统的信噪比提高了30～40dB。
2、本发明采用的单根大容量全同弱啁啾光纤光栅阵列无熔接点，无熔接损耗，提高传感距离。
3、本发明采用弹性材料的金属圆筒，具有较高的灵敏度和动态压力响应特性，对其上缠绕的光纤具有积极明显的增敏作用，并能够控制缠绕光纤的灵敏度，同时，也保证了啁啾光栅阵列光纤传感器的全光纤化(无熔接点)特征。
4、本发明采用的啁啾光栅阵列光纤制备在低损耗弯曲不敏感光纤上，在结构性增敏的同时减小弯曲带来的传输损耗，降低了对传 感距离的影响。
5、本发明采用的啁啾光栅阵列光纤是在低损耗弯曲不敏感光纤上在线刻写，类型为全同弱啁啾光栅，表现为反射光谱、反射率、有效带宽等特征参数基本一致。并且，啁啾光栅较于其他普通光栅(如感温光栅)，光谱较宽，3dB带宽达到4nm左右，较好地抑制了光谱温漂对水声检测的影响；目前还没有在水听器中使用啁啾光栅阵列的方案。
6、本发明利用干涉型分布式光纤光栅声学传感解调仪，采用短脉冲匹配干涉法解调得到每个光栅测区的相位变化信息，再通过每个光栅测区的相位变化信息线性还原得到每个光栅测区所感受的外界的水声声压的时间频率信息，定位能力强，解调灵敏度和精度高、速度快、实时性好。
附图说明
图1为本发明的结构示意图；
其中，1—干涉型分布式光纤光栅声学传感解调仪、2—啁啾光栅阵列光纤、2.1—啁啾光栅、2.2—奇数啁啾光栅测区、2.3—偶数啁啾光栅测区、3—金属弹性圆筒。
具体实施方式
以下结合附图和具体实施例对本发明作进一步的详细说明：
如图1所示基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，包括干涉型分布式光纤光栅声学传感解调仪1、啁啾光栅阵列光纤2和金属弹性圆筒3，所述啁啾光栅阵列光纤2中相邻两个啁啾光栅2.1之间的光纤构成光栅测区，光栅测区包括奇数啁啾光栅测区2.2和偶数啁啾光栅测区2.3，其中，奇数啁啾光栅测区2.2作为增敏区，紧密缠绕在金属弹性圆筒3上(增加单位面积上的传感器长度和密度来增加传感器的传感灵敏度)，偶数啁啾光栅测区2.3为了满足水听器长距离分布式检测需要，沿金属弹性圆筒3长度方 向直线布设(仅增加灵敏度(只缠绕)会牺牲检测长度，但是奇数增加灵敏度，偶数保证检测长度)，且啁啾光栅阵列光纤2中的所有啁啾光栅2.1位于沿金属弹性圆筒3长度方向同一直线上(这样设置能保证传感器的定位准确性)，干涉型分布式光纤光栅声学传感解调仪1的光学信号输出端连接啁啾光栅阵列光纤2的一端，啁啾光栅阵列光纤2的另一端打结悬空或者连接光纤终结器，这样能避免光纤尾端端面反射对系统产生的光强干扰。
上述金属弹性圆筒3优选空心不锈钢圆筒，空心不锈钢圆筒具有良好的化学稳定性和动态压力响应特性。
上述技术方案中，所述干涉型分布式光纤光栅声学传感解调仪1利用短脉冲匹配干涉法(具体为短脉冲匹配干涉法中的3×3耦合器相位解调法，解调频率为10kHz)对啁啾光栅阵列光纤2上的光栅测区进行独立干涉解调，解调得到每个光栅测区的相位变化信息(参考文献Zhengying,Li,et al."Simultaneous distributed static and dynamic sensing based on ultra-short fiber Bragg gratings."Optics Express 26.13(2018):17437-17446.)，再通过每个光栅测区的相位变化信息线性还原得到每个光栅测区所感受的外界的水声声压的时间频率信息，实现利用光纤达到水声探测的目的。上述解调形式具有解调灵敏度和精度高、速度快、实时性好等优势。
上述技术方案中，所述啁啾光栅阵列光纤2为低弯曲损耗啁啾光栅阵列光纤，该低弯曲损耗啁啾光栅阵列光纤由低损耗弯曲不敏感单模光纤上在线刻写形成，低弯曲损耗啁啾光栅阵列光纤中单根大容量(1000个以上的光栅数量)全同弱反射率啁啾光纤光栅阵列无熔接点(无熔接点保证了低损耗)，啁啾光栅2.1的类型为全同弱反射率啁啾光栅，全同弱反射率啁啾光栅的反射率小于-30dB，低弯曲损耗啁啾光栅阵列光纤的10圈半径为15mm的宏弯附加损耗≤0.2dB。
全同弱啁啾光栅较宽的反射带宽可以抑制外界温度变化对解调 光路系统的影响。所述全同弱啁啾光栅的光栅长度均相等，相邻两个全同弱啁啾光栅的光栅间隔均相等，这种等距(在一定误差范围内)全同弱啁啾光栅阵列一方面有利于水下目标的精确定位检测，另一方面，较于传统的基于瑞利散射效应的Φ-OTDR技术可以保证系统较高的信噪比。
上述技术方案中，啁啾光栅较于其它普通光栅(如感温光栅)，光谱较宽，全同弱啁啾光栅的光栅反射光谱的3dB带宽为1～6nm，能较好地抑制光谱温漂对水声检测的影响。
上述技术方案中，所述啁啾光栅阵列光纤2中的全同弱啁啾光栅等间距分布，并且，啁啾光栅阵列表现出参数指标全同性，即光纤上所有的啁啾光栅的反射光谱、反射率、有效带宽等特征参数一致，这样解调光路系统在光脉冲宽度、脉冲强度等光学参数调节上更加便利，同时保证了解调光路系统的可靠性和稳定性。
上述技术方案中，所述奇数啁啾光栅测区2.2缠绕光纤的轴向长度远小于偶数啁啾光栅测区2.3的长度，这样提高了增敏区对水声的增强效果，同时保证了水听器长距离分布式检测的需要。
上述技术方案中，缠绕光纤的缠绕疏密、松紧程度可通过预留一定长度的光纤进行调节，实现水听器的检测灵敏度根据缠绕方法(张力、疏密程度)在一定范围内可调。
上述技术方案中，基于低损耗弯曲不敏感单模光纤的低弯曲损耗啁啾光栅阵列光纤，采用缠绕弹性体的方法进行结构上的增敏，弯曲带来的损耗对传输距离的影响较小。
上述技术方案中，所述金属弹性圆筒3在水声作用下引起的形变直接转换为缠绕在上面的啁啾光栅阵列光纤2的轴向应变，根据光纤的相位应力应变模型，利用干涉型分布式光纤光栅声学传感解调仪1实时解调水声引起的相位变化信息，从而实现高灵敏度的声压信号检测，利用光纤轴向应变即光纤长度变化来实现水声探测，在低频段(10kHz以下)具有良好的动态响应能力。
一种基于低弯曲损耗啁啾光栅阵列光纤的声压检测方法，其特征在于，它包括如下步骤：
步骤1：将啁啾光栅阵列光纤2的一端连接干涉型分布式光纤光栅声学传感解调仪1的光学信号输出端，啁啾光栅阵列光纤2的另一端打结悬空或者连接光纤终结器；
步骤2：啁啾光栅阵列光纤2沿金属弹性圆筒3缠绕延伸，缠绕延伸的规则为啁啾光栅阵列光纤2中相邻两个啁啾光栅2.1之间的光纤构成光栅测区，其中，奇数啁啾光栅测区2.2作为增敏区，紧密缠绕在金属弹性圆筒3上，偶数啁啾光栅测区2.3为了满足水听器分布式拖曳需要，沿金属弹性圆筒3长度方向直线布设，且啁啾光栅阵列光纤2中的所有啁啾光栅2.1位于沿金属弹性圆筒3长度方向同一直线上；
步骤3：所述金属弹性圆筒3在水声作用下引起的形变直接转换为缠绕在上面的啁啾光栅阵列光纤2的轴向应变，根据光纤的相位应力应变模型，利用干涉型分布式光纤光栅声学传感解调仪1实时解调水声引起的相位变化信息，从而实现高灵敏度的声压信号检测。
上述技术方案的步骤3中，所述根据光纤的相位应力应变模型，利用干涉型分布式光纤光栅声学传感解调仪1实时解调水声引起的相位变化信息，从而实现声压信号检测的具体方法为：
所述干涉型分布式光纤光栅声学传感解调仪1利用短脉冲匹配干涉法对啁啾光栅阵列光纤2上的光栅测区进行独立干涉解调，解调得到每个光栅测区的相位变化信息，再通过每个光栅测区的相位变化信息线性还原得到每个光栅测区所感受的外界的水声声压的时间频率信息。
本发明利用金属弹性圆筒材料本身的动态压力响应特性，解决现有的光纤水听器中光纤本身对水下声压灵敏度不高的缺陷，通过增敏结构设计和结合干涉型分布式光纤光栅声学传感解调系统，极大地提高了声学传感的灵敏度(在较小程度影响检测长度的情况下， (奇数区域)的缠绕在相同长度下增加了光纤的响应长度，增加了灵敏度)。
本说明书未作详细描述的内容属于本领域专业技术人员公知的现有技术。

Claims (10)

  1. 一种基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：包括干涉型分布式光纤光栅声学传感解调仪(1)、啁啾光栅阵列光纤(2)和金属弹性圆筒(3)，所述啁啾光栅阵列光纤(2)中相邻两个啁啾光栅(2.1)之间的光纤构成光栅测区，光栅测区包括奇数啁啾光栅测区(2.2)和偶数啁啾光栅测区(2.3)，其中，奇数啁啾光栅测区(2.2)缠绕在金属弹性圆筒(3)上，偶数啁啾光栅测区(2.3)沿金属弹性圆筒(3)长度方向直线布设，且啁啾光栅阵列光纤(2)中的所有光栅(2.1)位于沿金属弹性圆筒(3)长度方向同一直线上，干涉型分布式光纤光栅声学传感解调仪(1)的光学信号输出端连接啁啾光栅阵列光纤(2)的一端，啁啾光栅阵列光纤(2)的另一端打结悬空或者连接光纤终结器。
  2. 根据权利要求1所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：所述干涉型分布式光纤光栅声学传感解调仪(1)利用短脉冲匹配干涉法对啁啾光栅阵列光纤(2)上的光栅测区进行独立干涉解调，解调得到每个光栅测区的相位变化信息，再通过每个光栅测区的相位变化信息线性还原得到每个光栅测区所感受的外界的水声声压的时间频率信息。
  3. 根据权利要求1所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：所述啁啾光栅阵列光纤(2)为低弯曲损耗啁啾光栅阵列光纤，该低弯曲损耗啁啾光栅阵列光纤由低损耗弯曲不敏感单模光纤上在线刻写形成，低弯曲损耗啁啾光栅阵列光纤中单根全同弱反射率啁啾光纤光栅阵列无熔接点，啁啾光栅(2.1)的类型为全同弱反射率啁啾光栅，全同弱反射率啁啾光栅的反射率小于-30dB，低弯曲损耗啁啾光栅阵列光纤的10圈半径为15mm的宏弯附加损耗≤0.2dB。
  4. 根据权利要求3所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：各个全同弱反射率啁啾光栅 的光栅长度均相等，相邻两个全同弱反射率啁啾光栅的光栅间隔均相等。
  5. 根据权利要求3所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：所述全同弱反射率啁啾光栅的光栅反射光谱的3dB带宽为1～6nm。
  6. 根据权利要求3所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：所述啁啾光栅阵列光纤(2)中的所有全同弱反射率啁啾光栅的反射光谱、反射率、有效带宽等特征参数均一致。
  7. 根据权利要求3所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：所述奇数啁啾光栅测区(2.2)缠绕光纤的轴向长度小于偶数啁啾光栅测区(2.3)的长度。
  8. 根据权利要求3所述的基于低弯曲损耗啁啾光栅阵列光纤的增强型水听器检测装置，其特征在于：所述金属弹性圆筒(3)在水声作用下引起的形变直接转换为缠绕在上面的啁啾光栅阵列光纤(2)的轴向应变，根据光纤的相位应力应变模型，利用干涉型分布式光纤光栅声学传感解调仪(1)实时解调水声引起的相位变化信息，从而实现声压信号检测。
  9. 一种基于低弯曲损耗啁啾光栅阵列光纤的声压检测方法，其特征在于，它包括如下步骤：
    步骤1：将啁啾光栅阵列光纤(2)的一端连接干涉型分布式光纤光栅声学传感解调仪(1)的光学信号输出端，啁啾光栅阵列光纤(2)的另一端打结悬空或者连接光纤终结器；
    步骤2：啁啾光栅阵列光纤(2)沿金属弹性圆筒(3)缠绕延伸，缠绕延伸的规则为低弯曲损耗光栅啁啾阵列光纤(2)中相邻两个啁啾光栅(2.1)之间的光纤构成光栅测区，其中，奇数啁啾光栅测区(2.2)缠绕在金属弹性圆筒(3)上，偶数啁啾光栅测区(2.3)沿金属弹性圆筒(3)长度方向直线布设，且啁啾光栅阵列光纤(2) 中的所有啁啾光栅(2.1)位于沿金属弹性圆筒(3)长度方向同一直线上；
    步骤3：所述金属弹性圆筒(3)在水声作用下引起的形变直接转换为缠绕在上面的啁啾光栅阵列光纤(2)的轴向应变，根据光纤的相位应力应变模型，利用干涉型分布式光纤光栅声学传感解调仪(1)实时解调水声引起的相位变化信息，从而实现声压信号检测。
  10. 根据权利要求9所述的基于低弯曲损耗啁啾光栅阵列光纤的声压检测方法，其特征在于：所述步骤3中，所述根据光纤的相位应力应变模型，利用干涉型分布式光纤光栅声学传感解调仪(1)实时解调水声引起的相位变化信息，从而实现声压信号检测的具体方法为：
    所述干涉型分布式光纤光栅声学传感解调仪(1)利用短脉冲匹配干涉法对啁啾光栅阵列光纤(2)上的光栅测区进行独立干涉解调，解调得到每个光栅测区的相位变化信息，再通过每个光栅测区的相位变化信息线性还原得到每个光栅测区所感受的外界的水声声压的时间频率信息。
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