Remotely-interrogated three-axis fiber laser magnetometer

A novel fiber laser magnetometer, designed for seabed-mounted surveillance arrays, is described. The sensor, comprising a metalized fiber laser attached to a nonmagnetic bridge, utilizes the Lorentz force generated in a magnetic field to detect small changes in the earth´s field. Three orthogonally mounted sensors measure each component of the field through high-resolution strain measurements, encoded as frequency shifts of the fiber lasers. The sensor node, incorporating three orthogonally mounted magnetic field sensors and a MEMS inclinometer, is qualified to an operating depth of 100 m and connected by a 1 km fiber-optic cable to the interrogation electronics.