Network Integration of Distributed Optical Fiber Temperature Sensor

The integration of distributed optical fiber temperature sensor with supervisory control and data acquisition （SCADA） system is proposed and implemented. In the implementation of the integration, both the compatibility with traditional system and the characteristics of distributed optical fiber temperature sensor is considered before Modbus TCP/IP protocol is chosen. The protocol is implemented with open source component Indy. The Modbus TCP/IP protocol used in the system is proved to be fast and robust.

Performance evaluation of two types of heated cables for distributedtemperature sensing-based measurement of soil moisture content

Distributed temperature sensing(DTS)using heated cables has been recently developed for distributed monitoring of in-situ soil moisture content.In this method,the thermal and electrical properties of heated cables have a significant influence on the measurement accuracy of soil moisture content.In this paper,the performances of two heated cables,i.e.the carbon-fiber heated cable(CFHC)and the metalnet heated cable(MNHC),are studied in the laboratory.Their structures,uniformity in the axial direction,measurement accuracy and suitability are evaluated.The test results indicate that the MNHC has a better uniformity in the axial direction than CFHC.Both CFHC and MNHC have high measurement accuracy.The CFHC is more suitable for short-distance measurement(500 m),while the MNHC can be used for longdistance measurement(>500 m).

A distributed measurement method for in-situ soil moisture content by using carbon-fiber heated cable

Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.

The Design of Fiber Bragg Grating Temperature Measurement System Based on Labview

The paper made a research on the fiber Bragg grating sensor demodulation system, which was based on virtual instrument labview and it developed a friendly upper monitor software. Based on the LM algorithm, the software realized rapid and accurate spectral data fitting, improving dynamic characteristics and measuring precision of the system. Depending on different fiber Bragg grating sensors, it can realize flexible calibration. It has the functions of collection, display and data storage, which can flexibly design alarm threshold according to the practical application. The fiber Bragg grating sensors can be identified by the software so that the distributed network, with large capacity optical fiber sensing, can be achieved.

Simulation of distributed optical fiber disturbance detection system based on Sagnac/Mach-Zehnder interferometer and cross-correlation location

A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system structure and location method are effective, accurate, and immune to environmental variations.

Highly sensitive optical fiber temperature sensor based on resonance in sidewall of liquid-filled silica capillary tube

A highly sensitive optical fiber temperature sensor based on a section of liquid-filled silica capillary tube(SCT)between single mode fibers is proposed. Two micro-holes are drilled on two sides of SCT directly by using femtosecond laser micromachining, and liquid polymer is filled into the SCT through the micro-holes without any air bubbles and then sealed by using ultra-violet(UV) cure adhesive. The sidewall of the SCT forms a Fabry–Perot resonator, and loss peaks are achieved in the transmission spectrum of the SCT at the resonant wavelength. The resonance condition can be influenced by the refractive index variation of the liquid polymer filled in SCT, which is sensitive to temperature due to its high thermooptical coefficient(-2.98 × 10^-4℃^-1). The experimental result shows that the temperature sensitivity of the proposed fiber structure reaches 5.09 nm/℃ with a perfect linearity of 99.8%. In addition, it exhibits good repeatability and reliability in temperature sensing application.

Novel Fiber Optic Temperature Sensor with Full Compensation Based on Optical Absorption

A novel system configuration of fiber optic sensor based on optical abso rption is proposed. Several compensation measures are discussed. A simulated exp eriment is designed and the output curve of system is given. The experiment al result shows that these compensation measures are effective on dynamic distu rbances which are caused by background light and optical fiber bend. In addition , the drifts in the light source intensity, fiber losses, and photodetector effi ciency are also compensated.

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.

Temperature measurement based on radialization power for micro-hotplate

A novel method to measure the temperature on the surface of micro-hotplate was presented. The tiny fiber probe and the optical power meter were employed to measure the sample radialization power. By means of comparing the relationship between the radialization power and the temperature, sample surface temperature can be discerned accurately. Such an approach has provided more accuracy than traditional temperature measurements. The experimental result based on this method is quite similar to that of simulation by the finite element analysis (FEA) software of Ansys in theory. This measurement is very useful for measuring temperature for these micro samples prone to be untouchable.

Technology of fiber-optic temperature sensing and its application in ＆ temperature measuring of gob area

Based on advantages of technology of distributive fiber-optic temperature sensing and specific to its applications in monitoring mine conflagration, the corresponding Processes such as connection arrangement, signal transmission and monitoring were illustrated. As applied in Sitai Coal Mine of Datong Coal Mine Group Co., this method is effective and accurate and could provide reliable gist for monitoring spontaneous combustion in gob area of mines.

New Measuring Temperature Setup with Optical Probe

Abstract: A new setup of measuring temperature is developed, which the probe is a micro- power consumptive one with CMOS circuit and is driven by optical power. For transmitting the measured signal and optical power signal in a long distance, the fiber technology is applied in this setup.

Development and Construction of 345 kV Power-Optical Fiber Composite XLPE 2,500 mm2 with Prefabricated Joint

Due to the increasing demand of replacing large capacity overhead lines with underground cables in Korea, KEPCO （Korea Electric Power Corporation） and LS Cable （LS Cable ＆ System） have developed 345 kV optical fiber composite XLPE （cross-linked polyethylene） 2,500 mm2 cable system. This system has been installed in Cheongna district of Incheon city. KEPCO and LS Cable are also planning to build the cooling system in a tunnel in order to reduce the ambient temperature caused by currents. In this paper, the process of development, field installation, and final inspection test of the complete system will be described.

Landslide Monitoring Based on High-Resolution Distributed Fiber Optic Stress Sensor

A landslide monitoring application is presented by using a high-resolution distributed fiber optic stress sensor. The sensor is used to monitor the intra-stress distribution and variations in landslide bodies, and can be used for the early warning of the occurrence of the landslides. The principle of distributed fiber optic stress sensing and the intra-stress monitoring method for landslides are described in detail. By measuring the distributed polarization mode coupling in the polarization-maintaining fiber, the distributed fiber stress sensor with stress measuring range 0 to 15 MPa, spatial resolution 10 cm and measuring range 0.5 km, is designed. The warning system is also investigated experimentally in the field trial.

Effects of seasonal air temperature variation on airflow and surrounding rock temperature of mines

In underground mines, high air temperatures in the summer months lead to an increase in inlet airflow temperatures. This leads to seasonal thermal pollution in the mines. This paper examines the dynamics and effects of seasonal variation in surface air temperatures and surrounding rock temperatures in deep coal mines. It also examines temperature variations in the main ventilation circuit, working face, and surrounding rock. The study results revealed that airflow temperatures were significantly affected by seasonal air temperature variations. The greater the distance was between the inlet and the wellhead of the ventilation shaft, the less the effect was on temperature. Moreover, slight temperature variations (1.0-3.0 ℃) were observed between various points on the return route during the summer months. Airflow temperatures along the airflow inlet to the return route of the working face first decreased, but then increased. The temperature field of the surrounding rock increased gradually with increased distance between the mine roadway and inlet, with recorded rock temperatures as high as 40.53 ℃. The radius of the heat-adjusting layer was between 28 and 33 m.

Distributed Discrimination of Strain and Temperature Based on Brillouin Dynamic Grating in an Optical Fiber

This paper reviews distributed discrimination of strain and temperature by use of an optical fiber based on fiber optic nerve systems. The preliminary method based on multiple resonance peaks of the Brillouin gain spectrum in a specially-designed fiber is firstly introduced. The complete discrimination of strain and temperature based on the Brillouin dynamic grating in a polarization maintaining fiber is extensively presented. The basic principle and two experimental schemes of distributed discrimination based on fiber optic nerve systems are demonstrated. The performance of the high discriminative accuracy （0.1 ~C-0.3 ~C and 5 kte-12~te） and high spatial resolution （-10 cm） with the effective measurement points of about 50 for a standard system configuration or about 1000 for a modified one will be highly expected in real industry applications.

浅谈配网自动化光纤通信系统施工技术

为了保证配网自动化光纤通信系统的稳定运行和信号的可靠传输,论文简要介绍了配网自动化光纤通信系统,对配网自动化光纤通信技术在施工过程中的施工要求、关键要点和注意事项进行了探究。

冻融条件下路基温度场和湿度场分布式感知试验

搭建土体冻融多物理场感知室内试验装置,布设传统点式传感器和分布式光纤,对土体冻融过程中路基温度场、湿度场和变形情况开展试验监测,探究单端冻结、双端融化条件下土体温度场和湿度场的分布式感知特征,验证主动加热分布式光纤技术的监测效果。试验结果表明,-15℃单端冻结条件下,土体冻结过程按降温速率分为快速冷却、逐步降温、稳定平衡三阶段,冻结锋面逐渐下移,最大冻深约占土柱高度的35%。孔隙水受冻胀迁移力影响向冻结锋面移动,引起冻融前后土体湿度场重分布,并导致土体冻胀变形,变形量为土体最大冻深的7.8%~10.9%。分布式光纤可准确得到冻融过程中土体温度场、湿度场变化特征,识别土体内冻结区域范围,温度、湿度监测拟合优度R2分别达0.98和0.94。

基于双斜坡法的光纤应变快速测量方法

为了提高基于布里渊散射的光纤应变测量的实时性,将仅根据两个工作点布里渊增益计算布里渊频移的双斜坡法用于光纤应变测量。介绍双斜坡法的基本原理,基于仿真布里渊谱研究左右两侧工作点选择对布里渊频移计算准确性的影响规律,确定最佳的工作点。基于确定的最佳工作点和不同信噪比的布里渊谱,研究信噪比(signal-to-noise ratio, SNR)对双斜坡法和最小二乘拟合法准确性的影响规律。结果表明:双斜坡法的两个工作点围绕光纤沿线布里渊频移的均值对称时误差最小;随两个工作点频率之差的增加布里渊频移误差先减小后增大。相似准确性下双斜坡法的布里渊谱测量时间仅为最小二乘拟合法的约1/30,布里渊频移的计算时间仅约为后者的1/480。

分布式光纤传感技术在水力压裂中的研究进展

分布式光纤传感技术作为最新的水力压裂监测技术,应用于各大油田的水力压裂过程中,并且能够实现实时监测,已取得了显著的应用效果。为使业界进一步了解不同类型传感技术的基本原理、理论模型研究进展、现场应用情况,从分布式光纤温度传感技术和声波传感技术在水力压裂过程中的监测基本原理出发,系统总结了各类传感技术的理论模型研究进展和在产液剖面、裂缝扩展形态监测等方面的应用现状,最后提出了未来分布式光纤传感技术的发展方向。研究结果表明:①分布式光纤传感技术可以利用温度或者声波信号转换得到周围环境温度或应变的变化情况,从而实现水力压裂过程中的实时监测;②与分布式光纤声波传感技术相比,温度传感技术的相关理论模型相对较为成熟,能够实现产液剖面及裂缝形态的相关计算;③分布式光纤传感技术主要用于水力压裂过程中压裂液的注入、裂缝扩展等方面的监测。结论认为:分布式光纤传感技术可以有效地推动中国非常规储层的勘探和开发,同时提高水力压裂效果评价技术水平,这对中国油气行业的可持续发展具有重要推动作用。

基于可重构分布式控温的高稳定度热控系统研究

随着光学遥感卫星分辨率的不断提高,光学系统的口径和焦距越来越大,空间光学系统对大面积、高稳定度温度控制的需求越来越突出,而集中控温模式存在热控引线多且走线困难、测温稳定性差等不足,难以满足光学系统大面积高稳定度的控温需求.提出了一种主控加远端的分布式控温系统构架和基于差分比例电阻的高稳定度测温方法,研制了基于分布式的可重构控温系统样机.试验结果表明:系统具有较强的拓展性和自主重构能力,大大提高了热控系统的适应能力,测温稳定性优于±3mK/3h.