Magnetic-field sensing with a single-mode fiber

A fiber-optic magnetic-field sensor is constructed by bonding a single-mode fiber to a nickel cylinder. The magnetic field, by means of the magnetostrictive effect, alters the state of polarization of light in the fiber. A sensitivity of 1.76 x 10(-2) rad/m Oe is demonstrated, permitting detection of fields as small as 4.4 x 10(-6) Oe/m of fiber.