共查询到20条相似文献,搜索用时 15 毫秒
1.
本文从粒子振动的角度讨论了光纤表面等离子体波传感器对于温度的敏感特性。对于金属 /介质的表面等离子体波传感器 ,在界面处产生的等离子体振动实质是大量电子的集体振荡。在某一特定的波长的P光激励下 ,电子吸收了光子的能量而改变了原来的运动方式 ,当激励的光信号与电子群的固有振荡频率一致时 ,大量的电子振动变为一种谐振。由于界面处的电子密度与温度是密切相关的 ,不同的温度时密度不同———温度越高 ,电子的密度越大 ,而电子群的集体振荡又与电子的密度密切相关。所以温度的变化将对等离子体的共振频率产生非常重要的影响。利用了这一效应来补偿环境介质的温度变化 ,可以克服环境温度对测试所带来的影响。此外 ,本文也讨论了采用光纤SPW传感器可以进行多参数的测量。 相似文献
2.
适用于硅微谐振器件测量的光纤位移传感器研究 总被引:1,自引:1,他引:0
对一种适用于硅微机械谐振器件测量的光纤位移传感器进行了研究,该光纤位移传感器探头采用了单根光纤探测形式和光纤“X”耦合器结构,在微弱光电传感信号处理上采用了“锁相放大器”提取方案,可以实现对静态位移和振动位移两种场合进行测量.对该传感器的实测结果表明:该传感器测量范围为0~100 μm,测量灵敏度3.95 mV/μm,精度等级优于1%,重复性优于0.5%.为作为应用实例,运用该传感系统对一种微悬臂梁硅微谐振器件进行了测量,成功提取了硅微谐振器件的微弱谐振信号,证实了该传感器可以实现对硅微谐振器件的非接触和无损测量,并具有非接触、易调试、高灵敏度等优点. 相似文献
3.
A simple optical fiber cantilever vibration sensor consisting of two opposite aligned bare optical fibers sealed in a quartz capillary is presented.The fiber with the longer bare section is suspended in air and acts as a cantilever.By detecting the transmission power of the sensor directly,the environmental vibrational frequencies and amplitudes may be obtained.By adjusting the cantilever's natural deflection angle,the sensor can achieve high sensitivity,good response linearity,and a wide dynamic range.Coupling conditions are optimized to minimize temperature effects by simply setting an appropriate air gap between the bare fibers. 相似文献
4.
5.
In this paper, a fiber optic sensor based on fiber Bragg grating (FBG) is employed to measure the ground vibrations which may be generated by earthquakes, debris flows, landslides, and rock impacts on the ground. The detected vibration signals were analyzed by both fast Fourier transform (FFT) and Gabor transform to obtain the frequency response. The performance of fiber optic sensor was examined and compared with the conventional ground vibration geophone sensor. From the results of field tests, the fiber optic sensor shows highly similarity with conventional geophone sensor for low frequency measurement. The fiber optic vibration sensing system presented in this research is appropriate for sensing ground vibration in the frequency ranges of 10–250 Hz. The sensor proved to be an alternative option for ground vibrations monitoring system. 相似文献
6.
与布里渊散射不同,石英光纤中斯托克斯拉曼散射与光纤所受应力无关,只是绝对温度的函数,而且其拉曼频移为1.395×1013 Hz, 比布里渊散射易于提取,作为分布式光纤温度传感器的传感信号有一定的优势,但斯托克斯拉曼散射信号比布里渊弱,其峰值功率在APD中产生的光电流在nA级,低于APD的噪声电流,经光电转换后信号的信噪比小于1,傅里叶变换以及小波变换都无法有效地处理这类信号。通过对斯托克斯拉曼散射信号进行特征分析后,采用累加与小波降噪的综合方法提取该信号,实现在APD噪声电流以下的超灵敏度探测,达到每度0.104 nA的温度灵敏度,低于本系统所有APD噪声电流2.3 nA的1个数量级。 相似文献
7.
A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric (MZI) detection technique is presented for interrogating laser frequency shift due to the measurand (piezoelectric transducer (PZT) is used to simulate the micro-vibration) induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal (0.03 rad near 2 kHz), the signal-to-noise ratio (SNR) of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 ×10^-5 rad/Hz1/2. 相似文献
8.
9.
Miniature optical fiber sensors with thin films as sensitive elements could open new fields for optical fiber sensor applications. Thin films work as sensitive elements and a transducer to get response and feedback from environments, in which optical fibers act as a signal carrier. A novel Ag coated intensity modulated optical fiber sensor based on refractive index changes using IR and UV-Vis(UV-visible) light sources is proposed. The sensor with an IR light source has higher sensitivity compared to a UV-Vis source. When the refractive index is enhanced to 1.38, the normalized intensity of IR and UV-Vis light diminishes to 0.2 and 0.8, respectively. 相似文献
10.
采用光线寻迹法分析微弯光纤传感器,指出其微弯临界周期即为光线以最大入射角在光纤内传播的空间重复距离,结论与耦合模理论分析及实验结果一致。 相似文献
11.
12.
Goossens J Martinez L Glorieux C Wilkie-Chancellier N Ehssein CO Serfaty S 《Ultrasonics》2006,44(Z1):e1179-e1182
Laser ultrasonic detection is a versatile and highly sensitive tool for the observation of surface waves. In the following study, laser ultrasonic detection is used for the experimental study of spurious normal vibration modes of a disk quartz sensor excited by a voltage pulse. The AT cut crystal (cut of the crystal relative to the the main crystallographic axis is 35.25 degrees) is optimal for generating mainly thickness-shear vibrations (central frequency 6 MHz) on the quartz surface. However, resulting from shear-to-longitudinal and shear-to-surface mode conversion, and from the weak coupling with the other crystallographic axes, other modes (thickness-compressional and bending modes) are always present in the plate response. Since the laser vibrometer is sensitive to normal displacements, the laser investigation shows waves that can be considered as unwanted for the AT quartz used as a shear sensor. The scanned three dimensional (3D) amplitude-space-time signals are carefully analysed using their representation in three dual Fourier domains (space-time, wave number-frequency). Results on the transient analysis of the waves, the normal bending modes and the dispersion curves are shown. 相似文献
13.
为了降低纵向换能器尺寸并提高发射带宽和发送电压响应,研究了一种弛豫铁电单晶/压电陶瓷混合激励换能器,换能器由[011]方向极化PIN-PMN-PT单晶和PZT-4压电陶瓷混合激励,利用多模态振动耦合的原理,通过单晶的32模式振动,可以灵活调整两种振子之间的驱动能力和刚度分配。首先通过四端网络法得到了换能器等效电路并计算了其谐振频率,然后利用有限元方法对换能器进行了仿真优化,最后制作了试验样机并进行了测试分析。换能器样机外径86 mm、长度80 mm,工作频带13~38 kHz,最大发送电压响应为144.9 dB,带内发送电压响应起伏小于6 dB,具有良好的宽带、小尺寸工作性能。 相似文献
14.
Ultrafast pulse sources based on multi-mode optical fibers are discussed. High-power passively mode-locked fiber lasers based on multi-mode rare-earth-doped optical fibers greatly exceed the power limitations of single-mode oscillators. Ultrafast multi-mode fiber amplifiers operating in conjunction with multi-mode oscillators provide even higher power levels, where nonlinear propagation effects enable pulse compression to below 100 fs. Multi-mode fiber oscillators can be combined with single-mode Raman-shifting fibers to produce widely wavelength-tunable sources of femtosecond pulses. Further amplification in Yb fibers allows for the generation of sub-100-fs pulses with W-level average powers. 相似文献
15.
16.
Lee YS Gardonio P Elliott SJ 《The Journal of the Acoustical Society of America》2002,111(6):2715-2726
This paper presents a theoretical and experimental study of the in-plane and out-of-plane coupling of a matched piezoelectric sensor/actuator pair bonded on a beam. Both the sensor and actuator are triangularly shaped polyvinylidene fluoride (PVDF) transducers and are intended to provide a compact sensor/actuator system for beam vibration control. The measured sensor-actuator frequency response function has shown an unpredicted increase in magnitude with frequency, which was found, to be due to in-plane vibration coupling. An analytical model has been developed to decompose the sensor-actuator response function into an in-plane contribution and an out-of-plane contribution. This in-plane coupling can limit the feedback control gains when a direct velocity feedback control is applied. A method called the j omega s compensation method is proposed to identify the effect of the in-plane vibration coupling at low frequencies. Even after this compensation, however, there was unexpected strong out-of-plane coupling at even modes, which may have been caused by a lack of accuracy in the shaping of the PVDF sensor and actuator. Numerical simulations have confirmed the sensitivity of the matched sensor/actuator pair with shaping errors. 相似文献
17.
The effects of stimulus frequency and intensity on response patterns (PST histograms) to tone burst stimulation were examined in differently tuned saccular fibers of the goldfish. In addition, the sensitivity of these fibers to amplitude-modulated (AM) signals of different carrier frequencies was measured. The response patterns evoked by unmodulated signals were a complex function of tuning, spontaneous activity and sensitivity of the fiber, and the frequency and intensity of the signal. Frequency-dependent response patterns were found in low-frequency fibers with best frequencies (BF) below 200 Hz. Responses in these fibers ranged from tonic to phasic in nonspontaneous fibers and included more complex patterns in spontaneously active fibers, such as suppression of evoked activity below spontaneous levels. Midfrequency fibers (BF = 500-600 Hz) showed responses similar to those in low-frequency fibers, but with less dependence on frequency. In contrast, both high-frequency (BF = 800-1000 Hz) and wideband, untuned fibers showed frequency-invariant patterns of adaptation. High-frequency fibers were equally sensitive to AM signals at all frequencies tested. The sensitivity of low-frequency fibers to AM, however, increased as a function of carrier frequency and corresponded to the degree of adaptation in response to unmodulated tones. In general, the AM sensitivity of a fiber could be predicted more by its pattern of response to unmodulated signals than by its tuning characteristics. 相似文献
18.
Simulations of the high-frequency modulation characteristics of semiconductor lasers with segmented contacts predict a pronounced resonance-like modulation response that is beyond five times the original cut-off modulation frequency. Based on an effective multi-mode Maxwell–Bloch model, the simulations reveal the underlying phenomena. They show that the high-frequency response is a direct consequence of the particular spatio-temporal and multi-mode dynamics induced by the segmented-contact laser geometry. 相似文献
19.
使用振声法探测埋地物体时,表层土壤松软导致地表振动传感器在耦合环节发生谐振, 造成谐频附近的信号失真,限制了所采信号的可用频段。针对传感器在水平方向的耦合谐振问题,该文研究了传感器质量对谐振频率的影响。仿真对比了传感器质量为2~250 g情况下信号采集系统的频响特征,并在季节性的冻土地表开展了对比实验与横波波速测量实验。仿真与实验结果表明:250 g传感器所对应的耦合谐频不超过800 Hz;2 g传感器的耦合谐频可超过1200 Hz;传感器质量越轻,耦合谐振频率越高,所采信号的可用频段越宽。 相似文献
20.
提出一种利用多模态耦合的开孔型宽带换能器。在传统纵振换能器前盖板一定距离处开一矩形通孔,以激发出能与纵振耦合从而拓宽频带的振动模态。以带宽为目标,利用有限元方法对通孔的长度、宽度和孔前端离前盖板端面的距离进行了优化设计,得到了最佳的开孔位置和尺寸。研制了换能器样机。测试结果表明,在12~32 kHz频带范围内,换能器有3个工作模态,后两阶模态对工作带宽的展宽有贡献。未开孔的同尺寸纵振换能器-3 dB带宽仅3 kHz,开孔换能器带宽则达10.50 kHz,有效地拓展了工作带宽。理论计算和测试结果吻合较好。 相似文献