Optical fiber magnetic field sensor with nanosecond response time

The attraction of optical fiber technology in the communications industry is the potentially huge bandwidths available. However, this unique characteristic does not appear to have been utilized in the development of new sensors. A new fiber based, magnetic field sensor with a potential bandwidth of several gigahertz is reported. The key element in this sensor is the magnetic semiconductor which uses the Faraday effect to detect the magnetic field. Polarized light passing through this material undergoes a rotation of polarization by an amount proportional to the magnetic field and the optical path length. With a polarizing analyzer this rotation is converted into amplitude modulation of the light.