Temperature-Insensitive Magnetic Field Sensor Based on an Optoelectronic Oscillator Merging a Mach-Zehnder Interferometer

A temperature-insensitive magnetic field sensor with high interrogation performance and large measurement range based on an optoelectronic oscillator (OEO) merging a Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated. In the OEO loop, a finite impulse response (FIR)-microwave photonic filter (MPF) and an infinite impulse response-MPF are cascaded to select the oscillating frequency and further suppress the side mode. The center frequency of the FIR-MPF, which is composed of a non-coherent broadband optical source, a MZI, a dispersion compensating fiber (DCF), and a photodetector, is determined by dispersion of DCF and the free spectral range (FSR) of the MZI jointly. In one arm of the MZI, a section of optical fiber is bonded with a giant magnetostrictive material (GMM) to achieve the magnetic field sensing, where the GMM is acted as a magnetic field-strain transducer. When the magnetic field varies, the FSR of the MZI will be changed, resulting in an oscillating frequency shift of the OEO. Therefore, a high interrogation performance magnetic field measurement can be achieved by simply monitoring frequency change of microwave signal generated by OEO in the microwave domain. Moreover, by placing a section of unprocessed fiber with appropriate length in the other arm of the MZI, the temperature cross-talk for the magnetic field can be alleviated greatly. In the experiment, the magnetic field sensitivity of 1.33 MHz/mT with a large range of 20.9 mT to 58 mT is obtained and the measurement error induced by temperature is as low as 0.09 mT.