All-fiber Current Sensor Using Nonlinear Optical Loop Mirror As The Reflector

With the development of modern society, all walks of life put forward higher requirements to the power system. The traditional electromagnetic transformer type current sensor have been unable to detect ultra high voltage, large current because of the disadvantages of large volume, high cost, poor insulation, hidden safety problems. As a new type of sensor technology, optical fiber current sensor is different from the traditional electromagnetic mutual inductance type current sensor, which has some advantages, such as:electrical insulation, anti electromagnetic interference, corrosion resistance, simple and sensitive device.After analyzing the advantages and disadvantages of various types of principles and structures of all-fiber current sensor, this paper proposes a new type of reflecting all-fiber current sensor using nonlinear optical loop mirror as the reflector, which based on detecting the polarization state changes of the output light. The relationship between the Stokes vector of light polarization and the current is derived, and a method in high-speed polarization detection is presented in the paper. In order to achieve all kinds of indexes of the sensor, this paper makes some required experiment components, including the signal light source, the polarization maintaining system, and the high-speed polarization detection system. All the components have been tested in a satisfied result. Then the sensor experimental platform is built, under the condition of loading0～200A AC, the sensor experiment has been tested. It comes a gratifying result which is consistent with the theoretical prediction, shows that the sensor has high measurement accuracy, which proves the feasibility of sensing structure and the experiment.