一种平面型光纤光栅水听器探头技术的研究

阐述了一种平面薄板结构的平面型光纤Bragg光栅(Fiber Bragg Grating,缩写为FBG)水听器探头的工作原理,从理论和实验上分析研究了该探头的结构灵敏度、频率响应特性以及加速度响应特性。平面圆形薄板采用不锈钢,尺寸为:直径15 mm、厚度0．15 mm,探头为圆柱型,尺寸为:直径17 mm、长20 mm。对于该尺寸结构的FBG水听器,探头静态灵敏度可达23 fm/Pa,比裸光栅增敏7300倍;谐振频率为6．5 kHz,而且幅频特性在100 Hz～5．5 kHz频率范围内较为平坦;低频段加速度响应灵敏度为:58～75(fm·s~2/m),在1 m/s~2加速度作用下其输出等效(2．52～3．26 Pa)压力作用下的输出。该结构的探头也便于多路复用组成水听器阵列。该平面结构不仅可以组成光纤FBG水听器探头,同样可以组成光纤光栅激光水听器探头。对薄板的几何尺寸进行适当的调整,可实现不同量程、不同带宽的水声压力测量。     

光纤Bragg光栅水听器特性及实验研究

论述了光纤Bragg光栅（FBG）水听器探头基元 （FBG）的传感特性,分析了FBG的耦合系数、反射率、反射带宽和栅长对光纤Bragg光栅水听器传感特性的影响.通过改进光纤Bragg光栅水听器探头封装结构,增加了其压力敏感系数.并将实验结果与标准水听器（压电型）比较,标定出光纤Bragg光栅水听器的声压灵敏度；对传感信号进行电路解调,得出了解调结果,结果显示与原始声波信号基本一致.试验表明,在1 kHz~25 kHz的声波检测范围,光纤Bragg光栅水听器响应平坦度好,信号输出稳定,证明文中采取的改进措施是有效的.     

新型光纤光栅水声传感器的研究

提出了一种新型的光纤布拉格光栅(FBG)水声传感探头结构以及光纤光栅传感信号的自解调方法。利用一对匹配光栅构成推挽结构,实现了传感-解调的合二为一,大大地减小了系统的复杂度;并通过筒状弹性体结构,解决了裸光纤光栅测量水声信号的灵敏度过小的问题,并具有温度补偿作用。仿真与初步实验结果表明,该水听器探头的测量动态范围超过100 dB,在100~200 dB re 1μPa的水声压范围内,测量灵敏度为0.36 nm/Mpa。     

光纤Bragg光栅水听器探头的特性及实验研究

论述了FBG水听器探头基元——光纤Bragg光栅(FBG)的传感特性,分析了FBG的耦合系数、反射率、反射带宽和栅长对FBG水听器传感特性的影响。通过改进FBG水听器探头封装结构,增加了其压力敏感系数。并将实验结果与标准水听器(压电型)比较,标定出FBG的声压灵敏度,在1～25KHz的声波检测范围,其响应平坦度好、信号输出稳定,改进措施是有效的。     

一种耐静压分布反馈式光纤激光水听器探头设计

大深度工作环境下，静水压会引起分布反馈式光纤激光水听器反射中心波长漂出解调系统的复用窗口，使水听器无法解调目标声压信号；不同的静水压也会引起分布反馈式光纤激光水听器灵敏度的变化，影响光纤激光水听器阵列的一致性。基于电力声类比理论，提出带静压补偿的分布反馈式光纤激光水听器探头，建立结构的声压传递函数，分析各结构参数对传递函数的影响，为分布反馈式光纤激光水听器探头频率响应平坦化设计提供理论依据。加工制作了耐静压分布反馈式光纤激光水听器样品进行测试，在0 kHz～10 kHz频率范围内声压灵敏度波动范围不大于±2.4 dB，2.3 MPa内出射激光中心波长漂移量不大于0.06 nm，对深水光纤激光水听器的研究具有指导意义。     

带加速度补偿的DFB光纤激光水听器

针对分布反馈式光纤激光水听器在用于水声探测时极易受加速度效应干扰的问题,设计了一种双膜片对称结构的光纤激光水听器,对该水听器的抗加速度性能进行了研究.建立了双膜片结构水听器的加速度灵敏度理论模型,分析了水听器各部件的尺寸大小、材料参量与水听器加速度灵敏度的关系,实现了对水听器结构的优化设计;加工制作了分布反馈式光纤激光水听器原型样品,并进行了实验研究.测量结果表明,在2.5~10kHz的频率范围内,该结构水听器的平均声压灵敏度为-132.6dB,波动幅度不大于±0.5dB,加速度灵敏度小于-28dB.该水听器在保证了较高声压灵敏度与平坦的响应曲线的同时,抗加速度性能也得了有效改善,可大大提高光纤激光水听器阵列在运动状态下对远距离目标探测的信噪比.     

聚合物边孔封装无源光纤光栅水听器

报道了一种聚合物边孔封装的无源光纤光栅水听器的研究结果.采用边孔封装结构对裸光纤光栅进行了增敏封装,其静态压力灵敏度提高了17120倍,为光纤光栅的水声探测奠定了物理基础;利用可调谐窄带光源的线宽窄和其波长可调谐的特点,采用带工作点控制的强度调制方案进行信号解调,不仅实现了高精度的动态信号检测,并解决了温度变化对系统影响的问题.实验测量结果表明,所设计的光纤光栅水听器在500Hz频率处的声压灵敏度为-153.3 dB(0 dB=1 pm/μPa),且具有非常好的各向同性指向性,其最小可测声压为61 dB(0 dB=1 μPa/√Hz).     

分布反馈式光纤激光水听器的声压灵敏度频率响应特性

光纤激光水听器的频率响应曲线会在声压传递函数的谐振频率处出现谐振峰,使水听器的工作频带变窄。研制了一种金属膜片端面增敏结构的分布反馈式(DFB)光纤激光水听器。基于电声类比理论,建立了DFB光纤激光水听器的声压传递函数模型,仿真分析了水听器各结构参数对水听器声压传递函数的影响,实现了水听器结构的优化设计,加工制作了水听器原型样品并进行了实验研究。由实验结果可知,DFB光纤激光水听器在2.5~10kHz频率范围内的平均声压灵敏度为-135.99dB,波动幅度小于±0.6dB,且在16kHz附近出现谐振峰,实验结果与仿真分析结果较好地吻合。该研究对DFB光纤激光水听器的研制具有重要指导意义。     

夹层式光纤激光水听器探头优化设计

为改善分布反馈式(DFB)光纤激光器水声探测性能,利用有限元软件ANSYS,以相对加速度灵敏度为目标函数,结构尺寸参数为设计变量,结构第一阶固有频率和探头声压灵敏度为状态变量,对夹层式封装结构进行了优化设计,对其声压探测及抗加速度机理进行了分析。分析表明,基于优化结果设计的探头在采用100m非平衡干涉仪时,其声压灵敏度约为-135.1dB,相对加速度灵敏度可达到-19.6dB。结果表明,基于封装结构敏感部分分别承受声压激励和加速度激励时的不同响应机理,对夹层式封装结构关键部位尺寸进行优化设计后,通过合理选择承压梁与中间变形梁的厚度以及上下连接点的位置,封装制得的光纤激光水听器具有较高的声压灵敏度和良好的抗加速度性能。     

一种有源型光纤水听器原理与实验分析

分析了一种有源型光纤水听器的水声传感原理,在一段掺铒光纤中写入具有π相移的光纤光栅构成光纤激光器,水声压力作用在激光器上引起激光波长的移位,采用干涉法检测出波长移位引起的相位变化即得到声压的信息.水声探测实验表明,有源型光纤水听器的声压灵敏度为-166.5 dB(参考值1 rad/μPa).将不同工作波长的四元光纤水听器串接于一根光纤内组成水听器阵列,使用带通波分复用器将阵列发出的激光分离至各独立通道后检测出相应的声压信号,测得水听器之间的级串扰小于-60 dB,且单元水听器水声响应的动态范围不受影响.     

Study of the planar optical fiber Bragg grating hydrophone probe with acceleration compensation

Since the probe acceleration response of a planar optical FBG hydrophone is very obvious and has an adverse influence on normal underwater acoustic pressure detection,an acceleration desensitization method employing an acceleration compensation measure is presented here.Results indicate that by utilizing this method,the equivalent pressure output applied by one unit of acceleration(1m·s^-2) is reduced from a range of 2.52-3.26 Pa to 0.0758-0.217 Pa, while the structural sensitivity decreases from 28 fm/Pa to 20 fm/Pa,however,the resonance frequency increases slightly from 6.2 kHz to 6.5 kHz.The increased resonance frequency helps to improve the dynamic frequency characteristics,and while the structural sensitivity is reduced, it can be compensated for by improving the optical FBG dynamic wavelength interrogation sensitivity.The system sensitivity of the optical FBG hydrophone is mainly determined by its wavelength interrogation sensitivity and not the probe structure sensitivity.Therefore,the acceleration compensation method would have broad practical applications.     

Research of the planar optical fiber Bragg grating hydrophone probe

This paper presents the planar Fiber Bragg Grating （FBG） hydrophone probe sensing principle, and theoretically and experimentally researches the probe structure sensitivity, the receiving sensitivity frequency response characteristic and the acceleration response property. Planar sheet is made of stainless steel, its thickness is 0.15 mm, its diameter is 15mm, and the length of hollow circular shell is 20 mm. For this size of the structure, the probe structure sensitivity is up to 23 fm/Pa, which is about 7300 times of the value of the bare fiber. The resonance frequency is 6.5 kHz, and the amplitude-frequency curve of the receiving sensitivity response is relatively flat within the frequency range of 100 Hz to 5.5 kHz. The output yielded by one unit acceleration （1m/s2） is equivalent to （2.52 to 3.26 Pa） acoustic pressure acting output. This probe structure is easy to form FBG hydrophone array by multiplexing technique. The research shows that this planar structure not only can form FBG hydrophone probe, but also can constitute optical FBG laser hydrophone probe. The structure can realize different bandwidth, different range acoustic pressure measurement by adjusting the geometrical size of the sheet.     

光纤光栅水听器技术实验研究

采用光纤布喇格光栅作为基本传感器件, 设计制作了光纤光栅水听器. 利用匹配光纤光栅解调技术, 实现了高灵敏度、高速度的动态信号测量, 并进行了相关的水下声音测量实验. 实验系统可测量水声信号频率范围为10 Hz~3 kHz, 测量动态范围为60 dB, 其结果具有很高的线性度.     

High-sensitivity,fiber-optic,flexural disk hydrophone with reduced acceleration response

Abstract

A hydrophone consisting of a hollow cylinder whose flexible, circular end plates are bonded to pairs of pat, spiral wound coils of optical fiber is described. When the end plate/disk is deformed due to a pressure difference, the outer and inner fiber coils experience opposite strains resulting in a “push—pull” optical path length difference which is detected in an all-fiber Michelson interferometer. The close proximity of the interferometric fiber coils, separated by the thin thermally conducting end plate, rejects thermal gradient-induced signals. The addition of a second identical end plate and fiber coil pair at the opposite end of the cylinder will double the acoustic sensitivity while canceling acceleration induced signals. The calculated and measured optical strain of a single simply supported plate, single-coil sensor (8.0 cm diameter, 3.0 mm thickness) using static pressure, acoustic pressure, and acceleration are in good agreement and yield a sensitivity of 0.21 rad/Pa (ΔΦ/ΦΔP = -301 dB re I μPa-1) below its resonance frequency of 3 kHz. The calculated and measured strain for a dual clamped disk (4.5 cm diameter, 1.0 mm thickness) acceleration-canceling sensor with four 8-m coils are in good agreement also and yield a sensitivity of 1.0 rad/Pa (ΔΦ/ΦpΔP = -291 dB re 1 μPa^?1) below the disk resonance frequency of 4.5 kHz. These are the highest fiber-optic, omnidirectional hydrophone sensitivities reported to date.     

High-sensitivity, fiber-optic, flexural disk hydrophone with reduced acceleration response

A hydrophone consisting of a hollow cylinder whose flexible, circular end plates are bonded to pairs of pat, spiral wound coils of optical fiber is described. When the end plate/disk is deformed due to a pressure difference, the outer and inner fiber coils experience opposite strains resulting in a “push—pull” optical path length difference which is detected in an all-fiber Michelson interferometer. The close proximity of the interferometric fiber coils, separated by the thin thermally conducting end plate, rejects thermal gradient-induced signals. The addition of a second identical end plate and fiber coil pair at the opposite end of the cylinder will double the acoustic sensitivity while canceling acceleration induced signals. The calculated and measured optical strain of a single simply supported plate, single-coil sensor (8.0 cm diameter, 3.0 mm thickness) using static pressure, acoustic pressure, and acceleration are in good agreement and yield a sensitivity of 0.21 rad/Pa (ΔΦ/ΦΔP = -301 dB re I μPa-1) below its resonance frequency of 3 kHz. The calculated and measured strain for a dual clamped disk (4.5 cm diameter, 1.0 mm thickness) acceleration-canceling sensor with four 8-m coils are in good agreement also and yield a sensitivity of 1.0 rad/Pa (ΔΦ/ΦpΔP = -291 dB re 1 μPa^-1) below the disk resonance frequency of 4.5 kHz. These are the highest fiber-optic, omnidirectional hydrophone sensitivities reported to date.