Special Spun Hi-bi Fiber And Its Applications In Fiber Optic Current Sensors

Fiber Optic Current Sensor(FOCS)is an equipment applying in industries like electricity industry aiming in current measurement,whose principle is based on Faraday effect and optic fiber technologies.It comes with more safe,compact size,no magnetic saturation,digital output interface and so on.It has many advantages,contrast to the traditional electromagnetic current transformer,and it will surely be the core equipment of Smart Grid in next generation.At first,the principle of Faraday effect and FOCS based on it are introduced,and the difficulties during the production of traditional narrowband wave plate is described.Broadband wave plate is introduced due to the problems with traditional ones.Contrast to the traditional ones,broadband wave plates are wavelength insensitive,temperature insensitive,and can be produced repeatedly.However,the length of the broadband wave plate itself is far more longer than the traditional ones,while it is also current sensitive,as a result,it may not satisfy the characteristics of the closed-loop of the current sensing fiber,so that the change of either the position of the current conductor to be tested or the magnetic field around the current sensing fiber may affect the measurement precision.Under such circumstances,two methods are proposed to optimize the anti-interference of the current sensing fiber,and the results are effective as expected in practical usage.For sensing fiber,the most important specification is the temperature characteristic,which is also the weakness of FOCS compared to.Two factors which may affect the temperature characteristic of the sensing fiber are analyzed,which are the pitch of the sensing fiber and the structure of the sensing fiber,and experiments have been done on variable types of fibers including PANDA fiber,elliptical core fiber and PM micro-structured fiber to study their temperature characteristics.