共查询到20条相似文献,搜索用时 31 毫秒
1.
A novel method for characterization of optical fiber resonators by an optical time-domain reflectometry (OTDR) technique is reported. This easy-to-use technique yields accurate results for cavity lengths ranging from a few meters to several kilometers. A simple relationship is established between the round-trip cavity loss and the position where the OTDR signal is maximum. The value obtained for the round-trip cavity loss turns out to be quite insensitive to uncertainties in the determination of the OTDR maximum position. 相似文献
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In this paper, we designed an optical fiber bidirectional strain gauge bonded on each single detecting point. Based on detecting single point of markedly different value from the remainder of the fiber, the loss-modulation approach is appropriately applied to monitoring the strain/deflection of pipelines in OTDR. It is worth noting that the distortion of pipelines can be measured partly by detecting the strain at the joint suitable to monitor gas trunk pipelines. The key technology for measuring both tensile strain and compressive strain is the pretreatment of bending the optical fibers on the two pairs of bending points, which can be identified by optical time domain reflectometer (OTDR) if inserting time delay optical fiber. 相似文献
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Chang-Yong Yun Dipesh Dhital Jung-Ryul Lee Gyuhae Park Il-Bum Kwon 《Optics & Laser Technology》2012,44(1):269-280
To prevent possible threats to public safety and economic loss from chemical leakage accidents, novel chemical sensing techniques for regular monitoring and leakage detection have been developed for various fields. We propose a fiber optic liquid chemical sensor (FOCS) system using specialty optical fibers and an optical time domain reflectometer (OTDR), and is based on the leaky wave mode sensing principle. OTDR enables simple multiplexing where individual sensor nodes along the fiber length could be interrogated by a common OTDR. The sensor node in the optical fiber is prepared by removing the desired length of a protective layer using mechanical stripping and chemical etching techniques. A novel laser stripping technique with superior capability to fabricate quasi-distributed dense sensor nodes is devised as well. The FOCS system is further analyzed to characterize the sensor response behavior in relation to the sensor node length and possible environmental and chemical temperature effect. Under the condition satisfying the leaky wave mode principle and within the minimum acceptable refractive index (RI) range by the system, this FOCS system could monitor numerous liquid chemicals with variable refractive indices and has been tested with positive results. In addition, the system shows the possibility for multi-point detection and is further expanded into a hybrid technique capable of estimating the refractive index range of the detected chemical. 相似文献
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The signal quality of a fiber-optic distributed temperature sensor based on optical time domain reflectometry (OTDR) is improved using a pre-filtering technique in the iterative deconvolution method. Investigation of the performance is proposed using iteration conditions in which recovery rate of the signal-component is equal to that of the unfiltering technique. The recovered signal in the pre-filtering technique gives a good signal-to-noise ratio (SNR), 3 times of the unfiltered signal. Consequently, improvements in the OTDR signal with SNR of from 10 to 100 are obtained under the iterations for both distance and temperature resolutions. 相似文献
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We describe both theoretical and experimental results obtained in an investigation of a new technique for increasing the dynamic range of 1.65-microm optical time domain-reflectometry (OTDR) systems. The technique utilizes delayed Raman amplification of a 1.65-microm signal pulse by a 1.53-microm pump pulse. Amplification occurs when the two pulses overlap, and this position is determined by the initial delay between the pulses and the fiber dispersion. An increase in dynamic range of 17.5 dB has been observed, and the OTDR backscattered Rayleigh signal was detected up to 100 km. No significant noise penalty is introduced as a result of the directionality of the Raman gain. 相似文献
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Y. Namihira Y. Horiuchi H. Wakabayashi T. Oshimi K. Kitagawa 《Fiber and Integrated Optics》1989,8(4):293-301
A Rayleigh backscattered signal and Fresnel reflection over a 167.6-km and a 251.2-km long pure silica-core fiber (PSF) with fiber loss 0.176 dB/km, and a 138.6-km and a 206.5-km long Ge-doped core dispersion shifted fiber (DSF) with fiber loss 0.218 dB/km have been observed with ultra-long-range optical time domain reflectometry (OTDR) using a 1.55-μm high-power semiconductor laser (LD) and InGaAs-APD with a low dark current at room temperature. The Rayleigh backscattered signal level and fiber loss are strongly dependent on the fiber dopant materials and fiber structural parameters. DSF gives a better SNR for short length fibers because the Rayleigh backscattered signal level is larger than PSF, but because the DSF loss is also larger, PSF gives a better SNR for fibers longer than the critical length. Accordingly, the dynamic range of OTDR in the different fiber types such as PSF and DSF becomes different. One-way backscattered dynamic ranges of 29.5 dB for the PSF and about 30.2 dB for the DSF at room temperature have been achieved. 相似文献
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Accuracy enhancement in Brillouin scattering distributed temperature sensor based on Hilbert transform 总被引:1,自引:0,他引:1
The scattering optical signal of OTDR based Brillouin scattering distributed sensor is very weak and have a frequency width of several decades megahertz, so it is hard to perform the traditional analogue coherent demodulation. A novel optical coherent detection based on Hilbert transform is presented here. In detail, Brillouin backscattering light is coherent detected with the reference light, which is modulated by microwave electric optical modulator to produce frequency-adjustable light, then the detected photocurrent signal is demodulated by digital signal processing based on Hilbert transform, and at last the distributed sensing signal with better S/N ratio is gained, which can enhance the performance of the sensor. The simulation and experimental results of the detection method are given. 相似文献
8.
基于经典小波变换的布里渊光时域反射计光信号处理 总被引:1,自引:0,他引:1
布里渊光时域反射计结构的布里渊散射分布式光纤传感器检测的是自发散射光,信号非常微弱,而且频带在几十兆赫兹以上,难以应用普通相干解调方法。针对传感散射光信号特点,提出基于经典(Morlet)小波变换的光相干检测方法。首先采用微波电光调制产生频移参考光和自发布里渊散射光进行相干检测,再应用经典小波变换进行散射光信号的幅度解调,得到信噪比改善的布里渊散射传感光信号。给出了数值模拟和实验数据处理结果,表明经典小波变换能较好地处理布里渊光时域反射计检测信号。并和基于希尔伯特(Hilbert)变换的传感信号处理方法进行了对比,发现此方法优于基于希尔伯特变换的信号处理。 相似文献
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Localization mechanisms and location methods of the disturbance sensor based on phase-sensitive OTDR
The mathematic models of the disturbance sensor based on phase-sensitive optical time-domain reflectometry (OTDR) are established. On the basis of the models, the localization mechanisms of the conventional location techniques for phase-sensitive OTDR are simulated. The simulation results indicate that the frequency characteristics of the backscattered signal at disturbance region are different from other regions. According to the results, a novel location method relied on power spectrum analysis is described. The experiment is then conducted over a monitored length of 9 km with a spatial resolution of 100 m, which demonstrates that the described location approach can significantly enhanced signal-to-noise ratio (SNR) to 19.4 dB. 相似文献
10.
Based on the microbend effect of optical fiber, a distributed sensor for real-time continuous monitoring of intrusion in application to buried pipelines is proposed. The sensing element is a long cable with a special structure made up of an elastic polymer wire, an optical fiber, and a metal wire. The damage point is located with an embedded optical time domain reflectometry (OTDR) instrument. The intrusion types can be indicated by the amplitude of output voltage. Experimental results show that the detection system can alarm adequately under abnormal load and can locate the intrusion point within 22.4 m for distance of 3.023 km. 相似文献
11.
We demonstrate a cost effective wavelength tunable optical time-domain reflectometry (OTDR) for wavelength division multiplexing passive optical networks (WDM-PON). In order to realize the unique wavelength tunable optical time-domain reflectometry (OTDR), the wavelength swept fiber laser was developed by a digital micro-mirror array device (DMD), and the correlation OTDR (COTDR) technique was used. We successfully detected the fault location at the remote node fibers with 20 m resolution and fast wavelength setting speed of ∼15 μs in conventional band (C-band). 相似文献
12.
Y. Namihira Y. Horiuchi H. Wakabayashi T. Oshimi K. Kitagawa 《Fiber and Integrated Optics》2013,32(4):293-301
A Rayleigh backscattered signal and Fresnel reflection over a 167.6-km and a 251.2-km long pure silica-core fiber (PSF) with fiber loss 0.176 dB/km, and a 138.6-km and a 206.5-km long Ge-doped core dispersion shifted fiber (DSF) with fiber loss 0.218 dB/km have been observed with ultra-long-range optical time domain reflectometry (OTDR) using a 1.55-μm high-power semiconductor laser (LD) and InGaAs-APD with a low dark current at room temperature. The Rayleigh backscattered signal level and fiber loss are strongly dependent on the fiber dopant materials and fiber structural parameters. DSF gives a better SNR for short length fibers because the Rayleigh backscattered signal level is larger than PSF, but because the DSF loss is also larger, PSF gives a better SNR for fibers longer than the critical length. Accordingly, the dynamic range of OTDR in the different fiber types such as PSF and DSF becomes different. One-way backscattered dynamic ranges of 29.5 dB for the PSF and about 30.2 dB for the DSF at room temperature have been achieved. 相似文献
13.
一个新型的基于全光纤Mach-Zehnder干涉仪BOTDR系统 总被引:10,自引:4,他引:6
报道了新型的分布式传感测量布里渊光时域反射(BOTDR)系统.布里渊散射频移和强度均依赖于温度和应变,因此,BOTDR利用光纤中的自发布里渊散射作为测量信号可以实现分布式温度和应变测量.在BOTDR中,光源采用窄谱半导体激光器,并由声光调制器调制成脉冲光,经掺铒光纤放大器放大后,注入测试光纤以产生自发布里渊散射.利用双通Mach-Zehnder干涉仪分离光纤背向散射中的自发布里渊散射与瑞利散射信号,实现了自发布里渊散射的直接检测.实验结果表明基于全光纤Mach-Zehnder干涉仪BOTDR方案是可行的. 相似文献
14.
The critical power of the input pulse in which spontaneous Raman scattering is not seriously disturbed by stimulated Raman scattering in a fiber optic temperature sensor has been investigated experimentally and theoretically. The critical power determines the critical distance, which is nearly equal to the distance where optical time-domain reflectometry (OTDR) signal of the stimulated Raman scattering becomes maximum. From this fact, a new method to determine the critical input power with the OTDR system has been proposed, which may be applicable to most distributed fiber optic temperature sensors. It has been determined that the critical power of the input pulse is 4 watts for an infinitely long silica fiber.Presented at the International Commission of Optics Topical Meeting, Kyoto, 1994. 相似文献
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A distributed optical fiber sensor (DOFS) with the principle of microbend loss has been developed for concrete or rock-sliding damage measurement. The combination of multiple microbend sensors can form a sensor array for distributed sensing application in monitoring local slippage or deformation along the rock mass of the high slope, and the optical time-domain reflectometry (OTDR) can be conveniently used for interrogation of each sensor point. The sensor sensitivity can be obtained at a specific range according to the requirement of the model test condition. Connected with multiplexed sensing processing schemes, its sliding range of dynamic sensing response reached 0–3.6 mm and semi-empirical formula was fitted according to data from model tests. The DOFS array may find a potential application in real-time monitoring and damage detection of large and critical slope engineering structures. 相似文献
19.
研制了一种混沌-脉冲混合信号光时域反射仪,其工作原理是通过连续混沌光与离散脉冲光分别对光纤中的菲涅尔反射与后向瑞利散射进行高精度测量,将2次测量结果进行线性叠加得到光纤故障测量曲线,该仪器解决了传统混沌光时域反射仪无法测量光纤损耗事件的问题。实验中利用G.652.B单模光纤作为被测对象,对该仪器进行了实际测试,测试结果表明:所研制的混沌-脉冲混合信号光时域反射仪在104 km测量范围内实现了与距离无关的35 cm空间分辨率测量,对光纤损耗事件也有良好的检测效果。 相似文献
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在光时域反射仪(OTDR)的测试原理基础上,提出了一种改善非反射事件定位精度的方法。根据这种方法,对光时域反射仪所采集的数据重新处理,利用光时域反射仪的注射脉部止升沿提高非反射定位的精度。 相似文献