Temperature self-compensative all-fiber magnetic field sensing structure based on no-core fiber cascaded with fiber Bragg gratings

A kind of fiber-optic magnetic field sensing structure based on no-core fiber (NCF) cascaded with fiber Bragg gratings (FBGs) is proposed. The NCF is sandwiched between two pieces of singlemode fibers to form singlemode-no-core-singlemode (SNS) interferometric fiber structure, which is cladded with the magnetic field sensitive material (i.e. magnetic fluid). Measurement is done by monitoring the differential intensity of the signal at the two Bragg peak wavelengths, which increases the magnetic field sensitivity and can decrease the cost of the pragmatic sensing system. Due to the similar thermal effect of NCF and FBG, the temperature cross-sensitivity is greatly reduced. The achieved magnetic field sensitivity is 0.1774 dB/mT at 0-6 mT and 1.9296 dB/mT at 6-18 mT. The temperature sensitivity is only 0.0623 dB/ degrees C in the range of 21-35 degrees C. The corresponding device does not necessitate intensity-stabilized broadband light source as well.