弱反射光纤光栅水听器拖曳线列阵

提出一种细尺寸、大孔径、高增益的弱反射光纤光栅水听器拖曳线列阵。根据匹配干涉方法选用反射率一致、中心波长相同以及3 dB带宽较宽的弱反射光纤光栅阵列;根据水声传感原理确定弱反射光纤光栅阵列的栅距以应用于5～10 Hz甚低频水声信号探测。采用光纤涂覆机对弱反射光纤光栅阵列二次涂覆,阵列中心波长整体一致漂移,栅距基本不变。采用扎纱机和护套机在二次涂覆弱反射光纤光栅阵列外铺设凯夫拉纤维和聚氨酯保护套形成水听器拖曳线列阵。测试拖曳线列阵水听器单元的声压-相位灵敏度在1 rad/μPa条件下分别为-136.97 dB@5 Hz、-139.64 dB@7.5 Hz、-139.36 dB@10 Hz;分析流噪声引起的水听器自噪声功率谱,拖速为8 m/s、频段为1～100 Hz的谱值在45～95 dB(1μPa~2/Hz)范围内。实验和分析结果表明,所提出的弱反射光纤光栅水听器拖曳线列阵甚低频段灵敏度高、流噪声低,有望增强无人航行器的甚低频水声信号探测功能。     

基于光纤水听器的声场水平相关性研究

中科院声学研究所声场声信息国家重点实验室与长沙国防科技大学合作研制出了一条32阵元的光纤水听器阵,并于2002年8月在渤海进行了一次海上实验。本文利用光纤水听器阵获得的气枪声信号进行了声场的水平相关性分析,并与理论结果进行了比较,实验和理论结果基本符合。     

分布反馈式光纤激光水听器拖曳线列阵实验研究

为了进一步增大光纤拖曳阵的探测距离,研制了缆径为16mm的32元分布反馈式光纤激光水听器拖曳线列阵.阵元在10~2 000Hz频率范围内的平均声压灵敏度为-142.7dB(re 1rad/μPa),波动幅度小于±2dB.基于声光调制器的时分、波分联合复用技术实现了32元光纤激光水听器的多路复用,各个阵元之间以及各个通道之间的串扰均小于-40dB,并完成了静态和动态拖曳湖上实验.实验结果表明,研制的32元分布反馈式光纤激光水听器拖曳线列阵无论是在静态,还是在6~16节的动态拖曳状态,都能对目标形成稳定的波束指向,与GPS轨迹记录完全一致,展现了分布反馈式光纤激光水听器拖曳线列阵在工程上的应用前景.     

矢量水听器线阵和弧线阵抗左右舷模糊性能分析

针对线阵声纳左右舷模糊问题,建立了基于矢量水听器直线阵 和 两种信息处理模式以及标量水听器弧线阵不同布阵方式的抗左右舷模糊性能数学模型,分析了不同布阵方式以及不同信息处理模式的抗左右舷模糊性能,并进行了仿真计算。分析和仿真结果表明,矢量水听器直线阵和标量水听器弧线阵在分辨左右舷性能和观察范围上各有优势。矢量水听器直线阵虽然可分辨左右舷且在作用距离上具有优势,但由于在一定扇面内分辨左右舷是依靠声纳方位历程图的明暗差异,在多目标情况下易造成声纳观察上的干扰;具有一定弧心角的标量水听器弧线阵,可以在更宽的扇面内具有抗左右舷模糊能力,但其以减小观察范围作为代价。     

矢量线阵和标量弧线阵抗左右舷目标模糊性能分析

针对线阵声纳左右舷目标模糊问题,建立了基于矢量水听器直线阵p+v_c和pv_c两种信息处理模式以及标量水听器弧线阵不同布阵方式的抗左右舷目标模糊性能数学模型,分析了不同布阵方式以及不同信息处理模式的抗左右舷目标模糊性能,并进行了仿真计算。分析和仿真结果表明,矢量水听器直线阵和标量水听器弧线阵在分辨左右舷性能和观察范围上各有优势。矢量水听器直线阵虽然可分辨左右舷,但由于在一定扇面内分辨左右舷是依靠声纳方位历程图的明暗差异,在多目标情况下易造成声纳观察上的干扰;具有一定圆心角的标量水听器弧线阵,可以在更宽的扇面内具有抗左右舷目标模糊能力。     

应用于拖曳细线阵的光纤水听器研究

研制了一种直径为13 mm的空气腔推挽式双臂对称补偿结构的光纤水听器,介绍了该光纤水听器的工作原理,优化设计了光纤水听器结构。在小直径情况下,保证了较高的声压灵敏度,同时获得了较低的加速度灵敏度。实验测得在80～2500 Hz频段内,该光纤水听器的平均声压灵敏度为-142.5 dB,灵敏度的起伏小于±0.8 dB,加速度灵敏度小于-20 dB。实验结果表明,研制的空气腔推挽式双臂对称补偿结构的光纤水听器,能很好地满足拖曳细线阵的使用要求。     

一种用于大坝混凝土声层析成像的水听器线阵

声层析成像技术可以用图像的方式精确完整地反映层析面上检测体内部质量,是一种有效的无损检测手段,在大坝混凝土的安全隐患检测中发挥着越来越重要的作用。本研究旨在研制成像用的接收声波的水听器线阵,该水听器线阵由12个水听器阵元组成,阵元间隔2 m,水听器由直径40 mm的接收型压电圆管和前置放大器组成。水听器在低于20 k Hz的频率范围内,自由场接收电压灵敏度为-173±3 d B,在2 MPa静水压力下灵敏度下降不超过2 d B。制作了2例具有清晰接收波形、一致性和可靠性好的水听器线阵,最终为客户在现场实地获得了高质量的层析图像。     

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.     

用垂直阵和单水听器测量水下目标辐射噪声的误差分析及其修正方法

文章给出了水声波导模型下垂直阵和单水听器测量水下目标辐射噪声的误差和修正方法,以便使两种测量结果一致和统一。在设定典型水声波导的参数后,用波数积分方法计算出声源到垂直阵各阵元的信道传输函数,再推导出垂直嵌套阵聚焦波束的信道传输函数,从而得到单水听器和垂直嵌套阵的测量误差。数值计算表明在70 m海深条件下,不同深度单水听器测量单频信号频谱级起伏达15 dB以上,总声级测量误差的均值为3 dB,而垂直嵌套阵测量单频信号频谱级起伏仅4 dB,总声级测量误差的均值趋于0 dB。海上实验测量单频信号声源级的结果与数值计算的起伏一致,海试中垂直阵获得较高的空间增益。结论是在浅海条件下垂直阵的测量精度高于单水听器的测量精度,用单水听器测量的目标总声级需要修正时可以修正,而用单水听器测量的单频信号声源级则难以修正。     

一种用于大坝混凝土声层析成像用水听器线阵

声层析成像技术可以用图像的方式精确完整地反映层析面上检测体内部质量,是一种有效的无损检测手段。在大坝混凝土的安全隐患检测中发挥着越来越重要的作用,本研究旨在研制成像用的接收声波的水听器线阵,水听器线阵由12个水听器阵元组成,阵元间隔2m,水听器由直径40mm的接收型压电园管和前置放大器组成,水听器在低于20kHz的频率范围内,自由场接收电压灵敏度为-173±-3dB,在2MPa静水压力下灵敏度下降不超过2dB。制作了二例了具有清晰接收波形、一致性和可靠性好的水听器线阵,最终为客户在现场实地获得了高质量的层析图像。     

Cymbal array: a broad band sound projector

A prototype 3 x 3 planar cymbal transducer array was built and tested. The array has a radiating area of 5.5 cm x 5.5 cm and a thickness of less than 8 mm. The measured transmitting voltage response was above 134 dB re 1 microPa/V @ 1 m and flat over the frequency range of 16 and 100 kHz. Array interaction was analyzed using an equivalent circuit model. The array interaction leads to variations in radiation resistance and velocity of the transducers in the array according to their surroundings in the array. The effect is enhanced overall efficiency and a flat response.     

Seabed geoacoustic characterization with a vector sensor array

This paper proposes a vector sensor measurement model and the related Bartlett estimator based on particle velocity measurements for generic parameter estimation, illustrating the advantages of the Vector Sensor Array (VSA). A reliable estimate of the seabed properties such as sediment compressional speed, density and compressional attenuation based on matched-field inversion (MFI) techniques can be achieved using a small aperture VSA. It is shown that VSAs improve the resolution of seabed parameter estimation when compared with pressure sensor arrays with the same number of sensors. The data considered herein was acquired by a four-element VSA in the 8-14 kHz band, during the Makai Experiment in 2005. The results obtained with the MFI technique are compared with those obtained with a method proposed by C. Harrison, which determines the bottom reflection loss as the ratio between the upward and downward beam responses. The results show a good agreement and are in line with the historical information for the area. The particle velocity information provided by the VSA increases significantly the resolution of seabed parameter estimation and in some cases reliable results are obtained using only the vertical component of the particle velocity.     

A transformation based method to design ultrasound array

In medical ultrasound imaging, the desired lateral field distribution at each focal distance can be obtained by optimal apodization. On the other hand, the lateral field is a function of focal distance. Hence, finding the optimal apodization is a very arduous process. To overcome this, we have introduced a suboptimal method by which optimal apodization can be calculated in any distance through a nonlinear transformation by the knowledge of the optimal one at a distance. This transformation is established on a fact that the lateral field distribution at focal distance can be expressed as the Fourier transform of a nonlinear function of the aperture weighting, instead of direct expression as the Fourier transform of the above. We have applied this method to map the apodization which obtains the desired beam pattern into the apodization which maintains the same properties on the lateral field distribution. For example, applying this method on a 50-elements λ/2 spaced linear array with length D has resulted in apodization that is optimal at distances D or D/2 by precision better than 9%. This method is useful especially in optimization problems, having no explicit constraint on the main lobe width, such as minimizing the sidelobe levels or minimizing main lobe width constrained to a predetermined value of sidelobe level. However, as the results show, this technique provides acceptable results in other cases.     

RIBLL终端大面积光纤阵列探测器研制

描述了RIBLL终端大型探测器之一的大面积闪烁光纤阵列探测器（LASFA）的工作原理和结构特点, 报道了LASFA的研制以及单元性能的改进与测试。 LASFA具有很高的时间分辨和空间分辨能力, 可以很好地测量RIBLL终端各种轻带电粒子的信息。 The principles and structure characteristics of Large Area Scintillating Fiber Array(LASFA) detector at RIBLL (Radioactive Ion Beam Line in Lanzhou) are described. The development of LASFA and the characteristics of the scintillating fibers unit are reported. LASFA can be used to detect the light charged particles at RIBLL terminal due to its good time and spatial resolutions.     

Four-wavelength DBR laser array with waveguide couplers fabricated using selective MOVPE growth

We have developed an integrated multiwavelength laser with waveguide couplers using a novel selective metal-organic vapor-phase epitaxy (MOVPE) technique. The lasing wavelength was controlled by modulating the effective refractive index of distributed Bragg reflector (DBR) waveguides. Array lasing wavelengths were distributed from 1548.0 to 1553.5 nm with an average spacing of 1.8 nm. The propagation loss of the waveguide coupler was about 16 dB for inner ports and 20 dB for outer ports with a 6 dB splitting loss. Four-wavelength laser outputs were coupled into a single-mode fibre.     

Application of cylindrical linear phased array in casing borehole

An Ultrasonic Phased Array （UPA） transducer is presented for borehole imaging and casing inspection in acoustical logging. First, a Cylindrical Linear Phased Array （CLPA）, which is made up of numbers of piezoelectric elements distributed on the surface of a cylinder uniformly, is designed and fabricated. By transmitting and receiving acoustic waves using different groups of elements under the control of the electric system, the CLPA can gcan all area of the borehole wall dynamically and rapidly. Then the radiation and reflection acoustic fields of the CLPA are investigated theoretically in the casing borehole with defects. Finally, the experimental researches about ultrasonic scanning and imaging for the casing boreholes with defects have been conducted by the CLPA transducer. The experimental results consist well with the theoretical ones.     

Pekeris波导中垂直发射阵的阵增益快速估计

为了利用单换能器的声强级估计垂直发射阵的声强级,研究了Pekeris波导中快速估计发射阵增益的方法。首先,基于等效深度简正波理论,计算了Pekeris波导中垂直发射阵的平均声强,进而得到用模态阶数求和表示的发射阵增益的表达式。然后对模态阶数用积分代替求和,并对引入的误差进行修,得到3/2次方衰减场区发射阵增益的快速估计表达式;有效声影区声场由于只剩1阶简正模态,可直接简化得到发射阵增益的快速估计表达式,在海底参数未知时可用海深近似代替等效深度来估计有效声影区的发射阵增益。计算机仿真和海上实验得到的阵增益快速估计误差均小于1 dB,验证了快速估计方法的有效性,这一发射阵增益快速估计方法可以为工程应用提供参考。      

Array size scaling of passive coherent beam combination in fiber laser array

Array size scaling of passive coherent beam combination is explored theoretically. The Strehl ratio variation with wavelength is simulated in 4-, 9-, 16-, and 25-channel fiber arrays. The average Strehl ratio and phase error are calculated. The Strehl ratio is found to be near 100% for arrays with less than 5 fibers, but decreases significantly for larger arrays. These results are in good agreement with the recent experimental results.     

声矢量圆阵相位模态域目标方位估计

为了实现矢量传感器在圆阵阵型下的应用,文中提出了一种适合于声矢量圆阵的目标方位估计算法。该算法首先将声矢量圆阵阵元域信号分解为一系列相互正交的相位模态,在相位模态域构造声压和质点振速的互协方差矩阵,然后进行MUSIC方位估计.理论分析和仿真结果表明,文中算法比相同阵型的声压阵MUSIC方位估计算法具有更好的噪声抑制能力、方位估计性能以及多目标分辨能力,试验结果也表明本文算法具有更好的噪声抑制能力以及更好的目标方位估计性能。该算法实现了声压和质点振速的相干处理,充分利用了声矢量传感器的平均声强抗噪原理,具有较强的抗各向同性噪声能力,并可以将子空间类DOA(Direction of Arrival)估计算法和相位模态域阵列信号处理技术有机结合起来,实现了声矢量传感器在圆阵阵型条件下的高分辨DOA估计。      

太阳辐射对溶解有机质荧光光谱特征的影响

利用三维荧光光谱研究了太阳辐射对溶解有机质(DOM)荧光光谱特征的影响。实验结果表明,太阳辐射使DOM的荧光发射光谱强度减弱。在三维荧光光谱图中,红枫湖样品的荧光峰A,C,南明河样品的荧光峰A,B,C,尤其是荧光峰C的λ_Exmax／λ_Emmax位置随着太阳辐射时间的延长而逐渐向短波长移动。从腐殖酸样品的三维荧光光谱图中则发现,原始样品荧光峰位置出现在λ_Ex／λ_Em=275/500 nm处,光照作用后出现两个荧光峰：λ_Ex／λ_Em=245/450 nm和310/450 nm。太阳辐射对DOM中不同荧光组分的光降解速率存在差异,从荧光峰A和C的比值r(A, C)随太阳辐射时间的变化趋势得知,荧光峰C比荧光峰A的荧光丢失速率更大,即对于太阳辐射作用更敏感。在整个光降解过程中,红枫湖、南明河DOM的r(A, C)值比标准腐殖酸Fluka HA的r(A, C)值的变化更显著。通过本研究表明,可以利用三维荧光光谱所提供的完整的光谱信息来研究DOM在光降解过程中的光谱特征以及物理化学组成等变化。