High sensitivity optical-fiber sensor for weak magnetic fields

An optical-fiber weak-magnetic-field sensor with sensitivity of 10 #755 Oe is reported. The device uses metal-glass as magnetostrictive material and an alternating-current phase tracking (PTAC) homodyne system for phase detection in an otical-fiber M-Z interferometer. Zeroing technique eliminates any problems arising from the magnetic hysteresis effects of the magnetostrictive material which affect its magnetometer output. The theory and design method of the transducer and the phase-detecting system are analyzed in detail