Detection of Low-Intensity Magnetic Fields with a Magnetostrictive Fiber Optic Sensor

his thesis presents the fabrication, evaluation, and performance results of a magnetostrictive fiber optic sensor. The sensor was fabricated using a Mach-Zehnder interferometric arrangement. Four classes of sensing arms were fabricate as ribbons, cylinders, sandwiches, and sputter coated sheaths. The four classes of sensing arms were evaluated using Metglas™ nickel, and a combination of Metglas™ and nickel. Optimization techniques were applied to the sensor to maximize its sensitivity. These techniques included annealing the magnetostrictive material, operating the magnetic field at a range of frequencies, enclosing the sensor in a shielded chamber, and fabricating the sensing arms with polarization maintaining fiber optic cable. The lowest magnetic flux density that could be detected was 0.3 mG. This was achieved using a Metglas™ ribbon-fiber configuration with the ribbons magnetization direction aligned perpendicularly with the applied 52 kHz AC magnetic field with a 5 volt DC bias. When operating this configuration at a 10 Hz AC magnetic field with a 5 volt DC bias, the lowest magnetic flux density that could be achieved was 8.9 mG