A Heterodyne Optical Fiber Current Sensor Based on a Nanowire-Grid In-Line Polarizer

A heterodyne optical fiber current sensor based on a nanowire-grid (NWG) in-line polarizer is proposed. The NWG is a one-dimension Au grating fabricated on a fiber tip by focused ion beam machining. Because the grating pitch is far smaller than the wavelength of the incident light, it works like an in-line transflective fiber polarizer with both the transmission and reflection light power being measured simultaneously. Based on this unique feature, an all-fiber optical current sensor is demonstrated. The heterodyne measurement makes it withstand light power variations showing good sensing stability. As an all-fiber sensor, discrete and bulky optical components are saved, making it more reliable in practical applications.