Phase drift compensation for electric current sensor employing a twisted fiber or a spun highly birefringent fiber

We propose a simple, passive signal-processing scheme to compensate for arbitrary phase shift in a Faraday-effect current sensor employing a twisted fiber or a spun highly birefringent fiber. The scheme is based on processing the ac and de components of the received signals with four detectors in a complementary manner to derive a stable signal that depends only on the Faraday rotation. The effectiveness of the scheme has been demonstrated with an experimental sensor for both twisted and spun highly birefringent fibers.