基于分布式光传感的输电线路地震信号分析

为了分析地震对输电线路的影响,利用OPGW分布式光传感监测系统采集了地震案例数据,对输电线路受地震影响时的振动进行了特征分析,并初步尝试以实测塔线体系振动数据开展地震对输电线路的影响程度评估,充分验证了基于光纤复合架空地线(OPGW)的分布式光传感监测系统可以准确监测到输电线路通道的地震活动,并能感知全线路受地震波的影响情况。

一种利用分布式光传感技术的变电站地基沉降监测方案

为了解决某些建设在地势低洼地区变电站的地基沉降问题,利用分布式光纤传感技术,提出了一种变电站地基沉降监测方案。在介绍分布式光纤传感技术的基础上,研究了抗干扰能力强的应力光缆作为感应元件。分别介绍了地表变形监测光缆、深部变形监测光缆、基桩沉降监测光缆和连接光缆的布设方式。最后以两种类型的变电站作为试点应用对象,对监测结果分析表明,由监测定位图中的波峰和波谷位置可以判断光缆松弛程度,进而确定应变方向和幅值,提出的监测方案可以很好地满足变电站地基沉降监测的需要。可以为变电站地基沉降防治技术的进步提供参考和辅助。

基于分布式光传感风速监测系统的输电线路通道强风侵袭追踪分析

利用安装在输电线路上的分布式光传感风速监测系统,通过分析风速时-空分布特征和变化趋势,捕捉到飑线风和台风对输电线路的影响,并实现其在输电线路通道运动轨迹的追踪分析:飑线风从线路大号端向小号端移动,影响时长不到2 h;而台风过境时线路长达30 km的档距段均处于结构清晰的台风眼中,约1 h后出眼区,风力骤增,并通过相应的预警机制进行判别预警。实测案例表明,基于分布式光传感的风速监测技术能够有效实时监控大风对输电线路的影响情况,为电力部门针对其范围及程度制定相应的运维措施提供第一手的数据支撑,也可为气象部门研究大风活动提供一种重要的数据来源。

单光纤分布式传感阵列接收响应特性分析

传统的单(光)纤分布式光纤传感处理方法是将其看作多个独立的“等效传感单元”,并对每个单元单独处理,未有效利用阵列增益扩大探测范围。针对此问题,对单纤分布式光纤水听器的接收响应进行建模仿真,结果表明当处理信号波长大于空间分辨率2倍时,在30°~150°开角范围内,各等效传感单元的频响起伏在3 dB内,且等效传感单元的输出强度与等效声中心处声场强度差异约在3 dB以内,相位响应基本与等效声中心处声场相位一致。此时,单纤分布式光纤水听器的接收响应可满足阵列处理要求,利用阵列增益可提高目标探测能力。

超长距离分布式光相位传感系统定位的一种新方法

针对超长距离分布式光相位传感系统对于被探测物理量的定位问题,提出一种双Mach-Zehnder(MZ)结构和相关算法相结合的信号定位新方法。研究结果表明,该定位方案可以成功地在长距离(50 km)的范围内对信号定位。传感系统埋设于地下0.5 m处时,可以得到最小定位相对误差为0.19%。

DISTRIBUTED MICROBEND FIBER-OPTIC STRAIN SENSOR

The distributed strain sensor has significant application in real time measurement of strain status for large and important engineering structures such as aircraft, bridge and dam. In this paper, a quasi distributed optical fiber strain sensor system is set up using optical time domain reflect technique. The local strain sensors based on a novel microbend configuration are designed and applied to measure local strains along the optical fiber. As the result of the experimental research, the microbend sensors show high sensitivity, good linearity and repeatability in certain operation range.

Distributed Optical Fiber Sensor for Multi-point Temperature Measurement

The distributed optical fiber sensing technology is overviewed,which is based on Raman scattering light theory.Basic operation principle,structure,system characteristics and signal processing are discussed.This structure and method of the signal processing possess of certain spatial resolution,hence will ensure the practicability of system.

Real-Time Distributed Fiber Optic Sensor for Security Systems： Performance, Event Classification and Nuisance Mitigation

The success of any perimeter intrusion detection system depends on three important performance parameters： the probability of detection （POD）, the nuisance alarm rate （NAR）, and the false alarm rate （FAR）. The most fundamental parameter, POD, is normally related to a number of factors such as the event of interest, the sensitivity of the sensor, the installation quality of the system, and the reliability of the sensing equipment. The suppression of nuisance alarms without degrading sensitivity in fiber optic intrusion detection systems is key to maintaining acceptable performance. Signal processing algorithms that maintain the POD and eliminate nuisance alarms are crucial for achieving this. In this paper, a robust event classification system using supervised neural networks together with a level crossings （LCs） based feature extraction algorithm is presented for the detection and recognition of intrusion and non-intrusion events in a fence-based fiber-optic intrusion detection system. A level crossings algorithm is also used with a dynamic threshold to suppress torrential rain-induced nuisance alarms in a fence system. Results show that rain-induced nuisance alarms can be suppressed for rainfall rates in excess of 100mm/hr with the simultaneous detection of intrusion events. The use of a level crossing based detection and novel classification algorithm is also presented for a buried pipeline fiber optic intrusion detection system for the suppression of nuisance events and discrimination of intrusion events. The sensor employed for both types of systems is a distributed bidirectional fiber-optic Mach-Zehnder （MZ） interferometer.

Recent Progress in Distributed Optical Fiber Raman Photon Sensors at China Jiliang University

A brief review of recent progress in researches, productions and applications of full distributed fiber Raman photon sensors at China Jiliang University （CJLU） is presented. In order to improve the measurement distance, the accuracy, the space resolution, the ability of multi-parameter measurements, and the intelligence of full distributed fiber sensor systems, a new generation fiber sensor technology based on the optical fiber nonlinear scattering fusion principle is proposed. A series of new generation full distributed fiber sensors are investigated and designed, which consist of new generation ultra-long distance full distributed fiber Raman and Rayleigh scattering photon sensors integrated with a fiber Raman amplifier, auto-correction full distributed fiber Raman photon temperature sensors based on Raman correlation dual sources, full distributed fiber Raman photon temperature sensors based on a pulse coding source, full distributed fiber Raman photon temperature sensors using a fiber Raman wavelength shifter, a new type of Brillouin optical time domain analyzers （BOTDAs） integrated with a fiber Raman amplifier for replacing a fiber Brillouin amplifier, full distributed fiber Raman and Brillouin photon sensors integrated with a fiber Raman amplifier, and full distributed fiber Brillouin photon sensors integrated with a fiber Brillouin frequency shifter. The Internet of things is believed as one of candidates of the next technological revolution, which has driven hundreds of millions of class markets. Sensor networks are important components of the Internet of things. The full distributed optical fiber sensor network （Rayleigh, Raman, and Brillouin scattering） is a 3S （smart materials, smart structure, and smart skill） system, which is easy to construct smart fiber sensor networks. The distributed optical fiber sensor can be embedded in the power grids, railways, bridges, tunnels, roads, constructions, water supply systems, dams, oil and gas pipelines and other facilities, and can be integrated with wireless networks.

Structural Health Monitoring by Using Fiber-Optic Distributed Strain Sensors With High Spatial Resolution

In this paper, we review our researches on the topics of the structural health monitoring （SHM） with the fiber-optic distributed strain sensor. Highly-dense information on strains in a structure can be useful to identify some kind of existing damages or applied loads in implementation of SHM. The fiber-optic distributed sensors developed by the authors have been applied to the damage detection of a single-lap joint and load identification of a beam simply supported. We confirmed that the applicability of the distributed sensor to SHM could be improved as making the spatial resolution higher. In addition, we showed that the simulation technique considering both structural and optical effects seamlessly in strain measurement could be powerful tools to evaluate the performance of a sensing system and design it for SHM. Finally, the technique for simultaneous distributed strain and temperature measurement using the PANDA-fiber Bragg grating （FBG） is shown in this paper, because problems caused by the cross-sensitivity toward strain and temperature would be always inevitable in strain measurement for SHM.

Wavelength Dispersion Analysis on Fiber-Optic Raman Distributed Temperature Sensor System

The influence of the wavelength dispersion on the temperature accuracy of the Raman distributed temperature sensor system （RDTS） is analyzed in detail, and a simple correction algorithm is proposed to compensate the fiber position error caused by the wavelength dispersion. The principle of the proposed algorithm is described theoretically, and the correction on each point along the entire fiber is realized. Temperature simulation results validate that the temperature distortion is corrected and the temperature accuracy is effectively improved from ＋5 ℃ to ±1 ℃.

Study of Optical Fibers Strain-Temperature Sensitivities Using Hybrid Brillouin-Rayleigh System

In this paper, the most recent progress as well as challenges of distributed optical fiber sensing （DOFS） in industrial applications is discussed. Compared to the vast market of sensors used to measure strain or temperature, the success of distributed optical fiber sensing （DOFS） at the industrial level is very limited, at best. One of the reasons for this lack of the wider acceptance is the mismatch between the commercially available systems and actual industrial requirements, especially for the spatial resolution and precision. These requirements are organized and clarified in the paper. It also describes the hybrid Brillouin-Rayleigh system, which exhibits capabilities surpassing those of strain gauges. The principles of the system are illustrated considering the fiber calibration methodology. Formulas required for determining strain, temperature, and hydro-pressure are derived and discussed. Finally, the examples of applications are presented.

A distributed optical fiber sensing system for synchronous vibration and loss measurement

We propose a fully distributed fusion system combining phase-sensitive optical time-domain reflectometry(Φ-OTDR) and OTDR for synchronous vibration and loss measurement by setting an ingenious frequency sweep rate(FSR) of the optical source. The relationships between FSR, probe pulse width and repeat period are given to balance the amplitude fluctuation of OTDR traces, the dead zone probability and the measurable frequency range of vibration events. In the experiment, we achieve synchronous vibration and loss measurement with FSR of 40 MHz/s, the proble pulse width of 100 ns and repeat rate of 0.4 ms. The fluctuation of OTDR trace is less than 0.45 dB when the signalto-noise ratio(SNR) is over 12 dB for a captured vibration event located at 9.1 km. The proposed method can be used for not only detection but also early warning of damage events in optical communication networks.

Single-/dual-wavelength switchable and tunable compound-cavity erbium-doped fiber laser with super-narrow linewidth

A single-/dual-wavelength switchable and tunable erbium-doped fiber laser(EDFL) with super-narrow linewidth has been proposed and experimentally demonstrated at room temperature. The fiber laser is based on a compound cavity simply composed of a ring main cavity and a two-ring subring cavity(TR-SC). Regardless of single- or dual-wavelength operation, the EDFL could always work well in single-longitudinal-mode(SLM) state at every oscillating wavelength. In dual-wavelength operation, the spacing could be tuned from 0 nm to 4.83 nm. In single-wavelength operation, the EDFL could lase at a fixed wavelength of 1 543.65 nm or another wavelength with a tunable range of 4.83 nm. The super-narrow linewidths of 550 Hz and 600 Hz for two wavelengths are obtained. The proposed EDFL has potential applications in microwave/terahertz-wave generation and high-precision distributed fiber optical sensing.

Design and Fabrication of a Novel Core-Suspended Optic Fiber for Distributed Gas Sensor

We designed a novel core-suspended capillary fiber that the core was suspended in the air hole and close to the inner surface of the capillary, and experimentally demonstrated its fabrication technology. In addition, a method for linking a single mode fiber and a core-suspended fiber was proposed based on splicing and tapering at the fusion point between the two fibers. By combining with the optical time domain reflectometer technology, we constructed a distributed gas sensor system to monitor greenhouse gas based on this novel fiber.

Distributed optical fiber vibration sensing system based on polarization detection

A novel distributed optical fiber vibration sensing system based on polarization detection is proposed and demonstrated. A Faraday rotator mirror is employed at the end of the system, which eliminates the slow polarization variation of signal light and only responses to rapid polarization change caused by external vibration interference. Based on the sensing signal characteristics, the location of polarization disturbance point can be detected accurately. Experiments on polarization controller simulation and actual vibration detection show that a higher localization accuracy better than 1% is successfully obtained in 13.8 kin, 21.2 km and 35.8 km sensing fibers systems.