Magnetic field sensor based on a dual-frequency optoelectronic oscillator using cascaded magnetostrictive alloy-fiber Bragg grating-Fabry Perot and fiber Bragg grating-Fabry Perot filters.

A magnetic field sensor using a dual-frequency optoelectronic oscillator (OEO) incorporating cascaded magnetostrictive alloy-fiber Bragg grating-Fabry Perot (MA-FBG-FP) and FBG-FP filters is proposed and demonstrated. In the OEO resonant cavity, two microwave signals are generated, whose oscillation frequencies are determined by the FBG-FP filter and MA-FBG-FP filter filters with two ultra-narrow notches and two laser sources. Due to the characteristics of MA and FBG, the two generated microwave signals show different magnetic field and temperature sensitivities. By monitoring the variations of two oscillating frequencies and the beat signal using a digital signal processor, the simultaneous measurement for the magnetic field and temperature can be realized. The proposed sensor has the advantages of high-speed and high-resolution measurement, which make it very attractive for practical magnetic field sensing applications. The sensitivities of the proposed OEO sensor for magnetic field and temperature are experimentally measured to be as high as -38.4MHz/Oe and -1.23 or -2.45 GHz/°C corresponding to the MA-FBG-FP filter and FBG-FP filter, respectively.