Optical Current Sensor Research Articles

Modeling and simulation of polarization errors in reflective fiber optic current sensor

Several key optical components in a reflective fiber optic current sensor (R-FOCS) show error characteristics, which induces linearly polarized light wave in polarization maintaining (PM) fiber and circularly polarized light wave in sensing fiber to be an elliptically polarized light wave. Therefore, nonreciprocal phase shift induced by magnetic field of the current is interrupted by the wrong polarization state. Focused on optical polarization error in R-FOCS, we analyze the characteristics of polarization errors associated with optical components in R-FOCS theoretically, and demonstrate the methods to build optical polarization error models by using Poincaré sphere and Jones matrix, respectively. Then, based on a model of polarization states in R-FOCS, we theoretically investigate the effect of several main error factors on optical polarization characteristics, including polarizing performance of polarizer, phase delay in quarter-wave retarder, splice angular between quarter-wave retarder and PM fiber, birefringence in sensing head and mirror reflection phase shift error. Finally, we quantify a nonreciprocal phase shift to be detected in R-FOCS with optical polarization error respectively, and propose measures.

Integrated Photonic Devices Incorporating Low-Loss Fluorinated Polymer Materials

Low-loss polymer materials incorporating fluorinated compounds have been utilized for the investigation of various functional optical devices useful for optical communication and optical sensor systems. Since reliability issues concerning the polymer device have been resolved, polymeric waveguide devices have been gradually adopted for commercial application systems. The two most successfully commercialized polymeric integrated optic devices, variable optical attenuators and digital optical switches, are reviewed in this paper. Utilizing unique properties of optical polymers which are not available in other optical materials, novel polymeric optical devices are proposed including widely tunable external cavity lasers and integrated optical current sensors.

The Nonreciprocal Errors in Fiber Optic Current Sensors

Nonreciprocal errors in fiber-optic current sensors, which are induced by environment fluctuations such as temperature and linear and angular vibrations, are specified. These errors in three current sensor configurations are evaluated and compared theoretically. The comparison indicates that the in-line sensor with strip waveguide modulator has the best resistance to the mentioned three environment fluctuations. Methods that may be used to suppress the nonreciprocal errors in different sensor configurations are suggested.

High sensitivity optical fiber current sensor based on polarization diversity and a Faraday rotation mirror cavity

A novel high sensitivity optical fiber current sensor (OFCS) based on polarization diversity and a Faraday rotation mirror cavity is proposed and demonstrated. Comparing with single-channel detection in a conventional OFCS, a signal power gain of 6 dB and a signal-to-noise ratio improvement of over 30 dB have been achieved in the new scheme. The cavity amplifies magnetic field-induced nonreciprocal phase modulation, while the Faraday rotation mirrors suppress the reciprocal birefringence. A linear response is obtained for current amplitude as low as several mA at an AC frequency of 1 kHz.

Functionality of bismuth sulfide quantum dots/wires-glass nanocomposite as an optical current sensor with enhanced Verdet constant

We report optical studies with magneto-optic properties of Bi2S3 quantum dot/wires-glass nanocomposite. The size of the Q-dot was observed to be in the range 3–15 nm along with 11 nm Q-wires. Optical study clearly demonstrated the size quantization effect with drastic band gap variation with size. Faraday rotation tests on the glass nanocomposites show variation in Verdet constant with Q-dot size. Bi2S3 Q-dot/wires glass nanocomposite demonstrated 190 times enhanced Verdet constant compared to the host glass. Prima facie observations exemplify the significant enhancement in Verdet constant of Q-dot glass nanocomposites and will have potential application in magneto-optical devices.

Test of fiber optic based current sensors on the Tore Supra tokamak

Fiber optic current sensors have been recently considered for current measurements in ITER. These sensors exploit Ampere's law by measuring the change of light polarization along an optical fiber subjected to a magnetic field aligned along the fiber axis. Through collaboration between CEA and SCK·CEN, such fiber optic current sensors have been installed on Tore Supra tokamak as a first demonstration for possible future applications in ITER. This paper aims at reporting the results obtained on Tore Supra. It discusses the technique used to separate the effects of the intrinsic linear birefringence and the magneto-induced circular birefringence, the latter enabling the determination of the current flowing through the area defined by the optic fiber loop. Three optical fibers have been installed on Tore Supra for assessment of their linearity response on a wide range of plasma current from 0.3 to 1.4 MA as well as their long term stability. The extrapolation of the results and the issues related to a future application on ITER are finally discussed.

A fiber-optic voltage sensor based on macrobending structure

We propose and demonstrate an optical voltage sensing scheme based on a macrobending optical fiber in a ratiometric power measurement system. This novel approach to sensing has not been utilized before and has the advantage that the sensor involves simple fabrication compared to existing fiber-optic voltage sensors. To prove the feasibility of such a fiber-optic sensor, a sensor for a voltage range from 0∼100 V is demonstrated, with a resolution of 0.5 V. The sensor is robust, linear, and shows a competitive measurement resolution. The sensor can be easily scaled to suit other voltage levels and be effectively combined with optical current sensors.

Optical fibre current sensor for electrical power engineering

Optical fibre current sensor for electrical power engineering

Evaluating a thermal image sharpening model over a mixed agricultural landscape in India

Fine spatial resolution (e.g., <300m) thermal data are needed regularly to characterise the temporal pattern of surface moisture status, water stress, and to forecast agriculture drought and famine. However, current optical sensors do not provide frequent thermal data at a fine spatial resolution. The TsHARP model provides a possibility to generate fine spatial resolution thermal data from coarse spatial resolution (≥1km) data on the basis of an anticipated inverse linear relationship between the normalised difference vegetation index (NDVI) at fine spatial resolution and land surface temperature at coarse spatial resolution. The current study utilised the TsHARP model over a mixed agricultural landscape in the northern part of India. Five variants of the model were analysed, including the original model, for their efficiency. Those five variants were the global model (original); the resolution-adjusted global model; the piecewise regression model; the stratified model; and the local model. The models were first evaluated using Advanced Space-borne Thermal Emission Reflection Radiometer (ASTER) thermal data (90m) aggregated to the following spatial resolutions: 180m, 270m, 450m, 630m, 810m and 990m. Although sharpening was undertaken for spatial resolutions from 990m to 90m, root mean square error (RMSE) of <2K could, on average, be achieved only for 990–270m in the ASTER data. The RMSE of the sharpened images at 270m, using ASTER data, from the global, resolution-adjusted global, piecewise regression, stratification and local models were 1.91, 1.89, 1.96, 1.91, 1.70K, respectively. The global model, resolution-adjusted global model and local model yielded higher accuracy, and were applied to sharpen MODIS thermal data (1km) to the target spatial resolutions. Aggregated ASTER thermal data were considered as a reference at the respective target spatial resolutions to assess the prediction results from MODIS data. The RMSE of the predicted sharpened image from MODIS using the global, resolution-adjusted global and local models at 250m were 3.08, 2.92 and 1.98K, respectively. The local model consistently led to more accurate sharpened predictions by comparison to other variants.

Methods to Describe Optical Polarization State in Reflective Fiber Optic Current Sensor

Evolution process of optical polarization state in reflective fiber optic current sensor(R-FOCS) is complex, light wave travels from polarization maintaining (PM) fiber with linear polarization state, and light wave travels from sensing head with circular polarization state. Focused on characteristics of optical polarization state in R-FOCS, we analyze the characteristics of optical polarization state in R-FOCS, and demonstrate the methods to build optical polarization models by using Poincare sphere and Jones matrix respectively. Jones matrix provides a mathematically rigorous method of tracking optical polarization state, however, it often leads to a less intuitive description. Despite the mathematical complexity of some phenomena observed in R-FOCS, the Poincare sphere provides elegant and simple geometrical interpretations. The two methods are combined and offer both a mathematical representation and an intuitive interpretation of nonreciprocal polarization effects in R-FOCS.

Optical Fibre Current Sensor for Electric Power Industry

The paper deals with the optical fibre current sensor based on new optical fibre made of glass with a high value of refractive index. This kind of glass was developed to meet the requirements of these optical fibres. The aim of investigations was to develop a new optical fibre with adequate magneto-optical properties and a relatively weak linear birefringence resulting from the process of its production. These features are of essential importance for optical fibre current sensors. The results of investigations concerning such optical fibres have been presented, displaying satisfactory magneto-optical properties, as well as only low linear birefringence induced by stresses arising in the course of their manufacturing.

Monitoring Method of Stray Current in Coal Mine on Optical Fiber Sensing Technique

In this work a novel monitoring method was developed to measure the underground stray current in coal mine with fiber current sensing technique. According to the theory of optical fiber current sensor based on Faraday magneto-optic effect, a fiber sensing system was designed and the relative experiments with current generator simulating stray current were completed. The results indicate that the measurement was influenced by birefringence and temperature change. The sensing heads with high cylindrical birefringence optical fiber had a good suppressing effect on linear birefringence and the polarization state of polarized light was also more stable than that with low birefringence optical fiber. The fiber current sensing method is doable in underground stray current monitoring system in coal mine.

Optical fiber microwire current sensor

We demonstrate a compact optical fiber microwire current sensor based on the Faraday effect with gigahertz frequency of current sensing capabilities.

편광회전 반사간섭계를 이용한 광전류센서

폴리머 광도파로를 기반으로 제작된 편광유지 3-dB 방향성 광분배기, 편광기, 위상 변조기 등의 광부품들을 이용하여 편광 회전 반사 간섭계형 광섬유 전류 센서를 제작하였다. 광섬유 전류센서를 위해 필요한 상기 광부품들을 개별적으로 설계 및 제작하여 특성을 확인하였으며, 전류 측정을 위해 사용되는 광섬유 센서 코일에서 발생되는 스트레인에 의한 복굴절을 제거하기 위하여 <TEX>$850^{\circ}C$</TEX>의 온도에서 24시간 동안 열처리를 실시하였다. 완성된 반사 간섭계형 광섬유 전류 센서를 이용하여 전선에 흐르는 전류의 크기를 측정하는 실험을 수행하였으며 전류의 양에 비례하는 안정적인 응답 특성을 확인하였다. Fiber optic current sensors based on polarization-rotated reflection interferometry are demonstrated by incorporating them into polymeric optical waveguide components, including polarization-maintaining 3-dB couplers, TE-pass waveguide polarizers, and thermooptic phase modulators. To remove the bending induced birefringence, optical fiber coil is annealed at <TEX>$850^{\circ}C$</TEX> for 24 hours. The reflection interferometry comprising polymer waveguide devices exhibit a highly stable output signal corresponding to the flowing current.

Development of a highly sensitive compact sized optical fiber current sensor

We have experimentally developed a highly sensitive and a compact size current sensor by using the CdSe quantum dots-doped bend insensitive optical fiber, operating in the visible band of wavelength. The modified sensitivity of this sensor was about 675 microrad/(Turn.A.m) for the loop radius of just 10 mm, which is more than 16 times larger than that of the single mode optical fiber current sensor.

Optical Current Sensors Consisting of Polymeric Waveguide Components

Optical current sensors are demonstrated based on polarization rotated reflection interferometry by incorporating polymeric optical waveguide components. Polarization maintaining 3-dB couplers, TE-pass waveguide polarizers, and thermo-optic phase modulators are designed and fabricated in this work in order to provide essential building blocks for constructing the current sensors. The phase difference between the two circularly polarized waves imposed by the Faraday effect of the optical fiber is detected using the interferometric optical sensor consisting of the polymeric components. To remove the bending induced birefringence, the optical fiber wound around a ceramic frame is annealed at 850 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C for 24 hours. The reflection interferometer comprising the polymer waveguide components operates with good linearity proportional to the monitoring current.

Development of Fault Detection System using Wavelength Division Multiplexing Transmission of Optical Fiber Current Sensor

A fault detection system is applied to power lines consisting of both overhead power line and underground power cable in order to detect a fault on the underground power cable section and prevent the automatic reclosing.The fault detection system using optical fiber current sensor has two subjects. The fist subject is that we have to use wound-type current transformer together, when applying the fault detection system to single-core underground power cable. The second subject is that we are not able to detect three-phase short-circuit fault in using the fault detection system.This paper describes that we developed a new fault detection system using optical fiber current sensor by applying the multiplex transmission technology of optical fiber current sensor signal in order to solve these subjects.

A Method for Improving Temperature Dependence of an Optical Fiber Current Sensor

This paper is described a method for improving temperature dependent properties of an intensity modulation type optical fiber current sensor for AC detection using flint glass fiber Faraday sensing element, which has been researched and developed by us. The sensor has highly advantageous properties such as light weight and flexible in various points of view, however, it also has a drawback that its output value is dependent on the ambient temperature where the sensor is installed. The ratio error in the sensor output value changes in the range of -0.4% to +1.2% corresponding to ambient temperature change of -20°C to +80°C. Its temperature dependent property is caused by the combined temperature dependence of a magnetic garnet crystal used in the sensor system and Faraday sensor fiber. We researched this temperature dependent mechanism and devised a gain adjusting method of the signal processing circuit amplifier to an optimum value to reduce the ratio error of the sensor. We verified that the ratio error was reduced remarkably with our method by experiment. The ratio error value obtained by the experiment was -0.1% to +0.2% in relation to ambient temperature change of -20°C to +80°C. This value met the highest accuracy standard for current transformers of protection relays required in JEC 1201-1PS class.

Novel optical fiber current sensor based on magnetic fluid

Novel optical fiber current sensor based on magnetic fluid

基于磁流体的新型光纤电流传感器研究

A novel fiber optic Fabry-Perot (F-P) current sensor is developed based on magnetic fluid as the medium in F-P interference cavity. A signal demodulation method based on slanted fiber Bragg grating (FBG) wavelength measurement system is proposed. Theory and principle of electromagnetic-controlled refractive index of the magnetic fluid is described, as well as the structure of the sensor system. Preliminary experiments are carried out, and the results indicate that there is a fairly good linearity of the measurement characteristic. The thickness of magnetic fluid film and initial concentration will affect the measurement results.