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The Research Of Re-entrent Fiber-optic Current Sensor

Posted on:2015-12-05Degree:MasterType:Thesis
Country:ChinaCandidate:P F LiuFull Text:PDF
GTID:2308330473451805Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Compared with the conventional electromagnetic current sensor, fiber-optic current sensor using optical fiber as the sensing medium has been greatly improved in the aspect of insulation, anti-electromagnetic interference, and reliability in recent years. However, because the performance of fiber-optic current sensor is based on the Faraday effects, the measurement accuracy is poor, and sometimes the measurement even cannot be done due to the introduction of much small Faraday effects, which limits its application fields.In this dissertation, In view of the characteristic of fiber-optic current sensor and the fact that the Faraday phase shift induced by the measured current is small, the structure and the operating principle of the ordinary fiber-optic current sensors using polarization detection has been firstly investigated theoretically and experimentally. And based on the investigation, a fiber-optic current sensors using optical fiber ring and polarization detection has been suggested. However, theoretical analysis and experimental results show that the polarization detection fiber-optic current sensor is strongly impacted by sensing fiber linear birefringence. therefore, based on Sagnac fiber-optic current sensors, a reentrant loop fiber-optic interferometric current sensors and a reflection reentrant cavity fiber-optic current sensor structure have been proposed. The effects of polarization errors caused by the two key components of the structure are analyzed and the experiments of proof-of concept have been done. The main contents of the dissertation are as follows:1. A study of the principles of ordinary polarization detection sensor fiber-optic current sensors is presented, and an experimental platform is set up for the experiment of proof-of concept. Based on the experimental results, the cause of measurement error is analyzed.2. A fiber-optic current sensors using optical fiber ring and polarization detection has been suggested. And theoretical analysis and experimental investigation have been done. However, the experimental results are not in good agreement with that of the theoretical simulation due to the limitations from the experimental conditions.3. By using Two Y-branch waveguide to instead of the commonly used fiber coupler, a re-circulating interferometric fiber optic current sensor is suggested. By settingthe appropriate Y-branch waveguide coupling ratio, the proposed sensor can achieve more times of light cycle in the sensing fiber, which means more induced Faraday phase shift. A corresponding sensor experiment platform is set up and the experimental results sre analyzed. In addition, the error of sensing system which introduced by the key components are investigated.4. An optical fiber reflective cavity using a Y-branch with one plated port and fiber mirror is proposed, which can increase the reflection times of light in the cavity so as to increase the induced Faraday phase shift, at last, to achieve the measurement of weak current. The theoretical analysis is presented and the error of sensing system which introduced by the key components are also investigated.
Keywords/Search Tags:current sensors, re-entrant, the Faraday effect, Y branch optical waveguide, optical fiber sensing
PDF Full Text Request
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