共查询到20条相似文献,搜索用时 578 毫秒
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Chen Rongsheng LIAO Yanbiao Zheng Gangtie Liu Tongyu Gerard Franklyn Fernando 《中国光学快报(英文版)》2001,10(3)
This paper reports, for the first time, on the use of a fused-taper single mode optical fiber coupler as a sensing element for the detection of acoustic emission (AE) and ultrasound. When an acoustic wave impinges on the mode-coupling region of a coupler, the coupling coefficient is modulated via the photo-elastic effect. Therefore, the transfer function of the coupler is modulated by an acoustic wave. The sensitivity of the sensor at 140 kHz was approximately 5.2 mV/Pa and the noise floor was 1 Pa. The bandwidth of the sensor was up to several hundred kHz. This AE sensor exhibits significant advantage compared with interferometer-based AE sensors. 相似文献
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A simple and low cost optical fiber acoustic sensor based on multimode-single mode-multimode (MSM) fiber structure is presented. The optical coupling efficiency between hetero-core fibers spliced structure is modulated by acoustic pressure through a thin metal foil. Acoustic wave is detected by measuring the intensity change of transmission light. Experiments are carried on to testify the performance of MSM fiber acoustic sensor and the experimental results show that the acoustic wave can be sensitively detected within 11 kHz frequency range. 相似文献
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声传感器和光声池是激光光声光谱技术的核心组件。结合光纤迈克耳孙干涉仪、相位载波解调技术和纵向共振光声池,提出一种共光声池腔的芯轴型空气衬底光纤麦克风。光纤麦克风中的铜毛细管被用作光声池的共振腔,传感臂由10 m长的超细光纤缠绕在铜毛细管上构成,参考臂为5 cm长的短臂且已进行隔声隔振处理。基于结构共振频率稳定的特点,优化光纤麦克风的共振频率,使其略低于光声池的一阶纵向共振频率,以实现准双共振。实验结果表明,麦克风在共振频率为1443 Hz处的最小可检测声压为0.69μPa√Hz。在1 kHz处,声压电压响应线性度为99.98%(5 mPa~3 Pa),动态范围为112.52 dB。该光纤麦克风适用于高温、易爆和高电磁干扰等特殊环境下痕量气体的高精度检测。 相似文献
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A fiber optic acoustic emission sensor based on fused-tapered coupler and its applications in structural health monitoring are proposed in this paper. The fiber optic acoustic emission sensor (FOAES) was tested using pencil lead break tests compared with the commercial acoustic emission sensor (R15 PZT). Besides, the sensor was embedded into the carbon fiber reinforced plastics (CFRP) materials and tested in the same way. It successfully detected the AE signals. FOAES was applied in the structural health monitoring (SHM) of CFRP materials. Damages of carbon fiber/epoxy composite laminates during three-point-bending test were monitored by surface-mounted and embedded FOAES, respectively. Results identified that the sensor embedded into composite structures could monitor damage of composite laminates on-line as the surface-mounted sensor did. 相似文献
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Abstract This study proposed and demonstrated a fiber Bragg grating sensor for simultaneous detection of the temperature and refractive index of a liquid. The fiber Bragg grating is composed of three index layers: an inner core, an outer core, and a cladding. The cladding was etched for evanescent wave coupling between the outer core mode and an external liquid. The Bragg wavelength of the inner core mode is used for obtaining temperature data, while the refractive index for the liquid was determined by using the difference between the Bragg wavelength of the inner core mode and that of outer core mode. 相似文献
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The experimental results of a conical piezoelectric transducer with integral backing sensor as a self-calibrating simulated acoustic emission (SAE) energy source are presented. It has been shown that there is a negative linear relationship between the energy of SAE signal detected by the backing sensor and the relative strength (signal energy) of SAE source in the structure detected by a reference sensor under different transducer-to-structure coupling efficiencies, with AC drives of the same wave packet, frequency and peak amplitude to excite the conical transducer as a SAE source at all the investigated frequencies over the frequency range of interest in AE measurements (nominally from 50 kHz to around 1 MHz). This should enable the relative strength of the SAE source in a structure to be determined using the SAE measurement from the backing sensor for the selected electrical inputs to the conical transducer, and hence to remove the concerns about inconsistent transducer-to-structure coupling affecting the relative strength of the SAE source for calibration. 相似文献
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近年国外出现一种直接检测弯曲的低成本光纤曲率传感器,采用弯曲增敏技术提高光纤对弯曲的灵敏度。这种传感器的线性范围宽,能区分正向弯曲和负向弯曲,在测量较大弯曲变形的场合更具优势;并且适合埋入结构内部检测,通过转换还可测量轴向应变。然而其传感机理方面的研究仍处于探索阶段。通过分析光辐射度余弦定律理论、回音壁光线理论、沟槽角度理论等国内外对该传感器机理的研究成果,并基于平面波导的光散射损耗理论,提出了光纤曲率传感器的机理。指出弯曲引起光纤敏感区表面散射损耗的改变是导致光传输损耗改变的原因;推导出损耗与光纤弯曲半径、表面特性、光纤结构参量关系的数学模型,并通过实验验证了模型的有效性。 相似文献
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干涉型长距离分布式光纤传感系统 总被引:6,自引:0,他引:6
提出了并验证了一种新型的以迈克耳辽干涉为基础的调频连续波干涉型长距离分布式光纤伟系统,系统在干涉仪的参考回路巧妙地引入了一个带有移频器的光学回路,使系统连续测量范围增加到4倍,达48m。 相似文献
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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. 相似文献
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Underwater Acoustic Sensor with Fiber Bragg Grating 总被引:1,自引:0,他引:1
A new type of underwater acoustic sensor is proposed with an optical fiber Bragg grating (FBG). Because of the photoelasticity with respect to the refractive index and the elasticity of the fiber, the sound pressure in water modulates the Bragg reflection wavelength and, in turn, the intensity of the laser light transmitted through the FBG fiber. Good linearity between the detected signal and the sound pressure is obtained in the range from 81 dB to 140 dB re 1 μPa. Since the upper and lower limits of the acoustic signal level for operation of the sensor are limited by the driving circuit and the transduction of the sound in water, the sensor is expected to operate with much larger dynamic range both at higher and lower pressure levels. Operation of the sensor is very stable with the insertion of optical isolators into the system, although without the isolators the output signal fluctuates at low frequency due to the Fabry-Perot interference effect between the FBG and the various facets. 相似文献
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为了拓宽光纤耦合器的使用范围,开发光纤耦合器的新功能,采用熔锥技术制作波长敏感耦合器,该耦合器在分光的同时对波长敏感。通过耦合理论验证实验结果,实验数据与理论值相符合。实验中得到波长灵敏度最大值为17.86%/nm的耦合器。采用拉锥工艺制作波长敏感耦合器工艺简单,耦合比峰值对应波长控制易于实现。该耦合器可用于光纤光栅布拉格波长漂移解调。令待解调光纤光栅布拉格波长与耦合器波长灵敏度最大值对应的波长一致,当波长发生漂移时,耦合器输出耦合比发生变化。自制的波长敏感耦合器实现了对布拉格波长为1566.71 nm光纤光栅波长漂移的解调,波长漂移1.80 nm,耦合比变化20.34%。此种解调方式具有光路简单,易于与光纤匹配的优点,可以应用在大型建筑中光纤光栅的健康监测。 相似文献
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High-performance unidirectional electrooptic modulator based on polymeric highly multi-mode waveguides 总被引:1,自引:0,他引:1
David Sun Xuejun Lu Dechang An John Taboada Lin Sun QingJun Zhou Jeffery Maki Suning Tang Ray T Chen 《Optics & Laser Technology》1998,30(8):481-489
A unidirectional electrooptic modulator based on an asymmetrical highly multi-mode waveguide coupler is proposed. Firstly, the energy distributions of all the modes within two highly multi-mode waveguides are analyzed with eigenstate theory. Then, to achieve high switching performance in a guided-wave coupler, a dumping wall is placed on the larger waveguide of an asymmetric pair of waveguides, so that the larger waveguide has a dumping effect. This dumping effect makes the asymmetric highly multi-mode waveguide coupler possess a highly efficient unidirectional coupling process. Due to the large cross-section of the waveguide, a new modulation electrode structure is built. Based on this dumping effect, the unidirectional coupling process is theoretically modeled. Furthermore, in both scenarios, i.e., the unmodulated state and the electrooptically modulated state, the unidirectional coupling efficiencies are studied. As a result, not only can a high unidirectional coupling efficiency of 100% be achieved, but a high electrooptic modulation depth more than 90% can also be implemented in theory, and a high thermooptic modulation depth more than 90% under a low modulation voltage of 30 volts is also experimentally achieved. This device can be used for multi-mode optical interconnection systems such as data communication and fiber sensor networks. 相似文献