Measurement of the linear birefringence inside bulk glass current sensing elements with a retarder

Linear birefringence inside the sensing head can obviously affect the performances of optical (fiber-optic) current transformers. Therefore, it is important to measure the linear birefringence for the design and the property enhancement of optical current transformers. A method employing a retarder to measure the linear birefringence inside the bulk glass current sensing head is reported. The theoretical analyses of the principle and the measurement uncertainty of the method are given using Jones Matrix as a mathematical tool. An applied example is also given. The main advantage of this method is that it can uniquely determine the value of the linear birefringence inside the sensing head, which overcomes the shortcoming of that only a trigonometric function value of the birefringence can be determined by the method reported before. Furthermore, there are some other advantages such as simple structured, practical and that the devices needed are easy to obtain.