Magnetic field biasing in Faraday effect sensors

A method for improving the performances of Faraday effect sensors, which is based in the passive magnetic field biasing of a Faraday rotator, is descr ibed. It allows obtaining reflective optical fiber sensor architectures, ba sed on a single polarizer and a mirror-coated Faraday rotator, which exhibi t linear response and maximum sensitivity. It can be achieved by means of a permanent magnet providing a 45 degrees rotation of the polarization of th e optical beam propagating through a Faraday rotator. Operation of this met hod in both a point magnetic field sensor and a current sensor, with a ferr omagnetic ring as concentrator, has been demonstrated. (c) 1999 American In stitute of Physics. [S0003-6951(99)04224-2].