Fiber optical sensors used for electric current measurement have been widely discussed [22]. Many theoretical or experimental results of fiber optic current sensors have been obtained. Optical fibers based on all-fiber Mach–Zehnder interferometer have been utilized to measure electric current, in which the phases of interferometric lights in the interferometer is modulated by utilizing heat effect caused by current flowing through a thin metal tube [23]. Fiber optical sensors based on birefringence characteristics [24], multiplexed interferometric sensors [25] and fiber Fabry–Perot interferometer [26] are also been used to measure electric current. Electric current also can be measured by FBG sensors in the presence of some mechanical transducers [27]. However, most of the above electric current measurement methods need complex system or follow-up expensive analytical equipments. Besides, electric current measurement accuracy of some methods is influenced by external environmental factors, such as temperature.