In-line Sagnac interferometer current sensor

We demonstrate for the first time a near shot noise limited in-line Sagnac interferometer current sensor. It is shown to have a number of advantages over the optical current sensols baTed on polarimetric Faraday and Faraday/Sagnac loop interferometer topologies, including lower sensitivity to environmental disturbances, less demanding optical con~ponenta~n, d easy installation.