Fiber-optic AC current sensor using metal coated intrinsic FFPI and silicon micromachining technology

We present an optical current sensor for using in a harsh environment. A metal coating is plated onto the optical fiber as a heater to measure the AC electrical current. The metals used are Au and Ni-Cr. The detection method for the electric current is based on a metal film heater with a fiber-optic Fabry-Perot interferometer (FFPI). When the sensor is subjected to time-varying temperatures, a phase shift, induced as a result of Joule heating, can be observed. For each metal, we measured the sensitivity of the sensor for AC electric current from 0 mA to 35 mA in the coated sensor. The sensitivity of the Au sensor appeared to be about 15.92 degree/mA and of the Ni-Cr sensor, about 39.43 degree/mA. The temperature dependency of the sensor is measured at about 2.41 degree/°C.