In order to mitigate the risk of measurement drift during long plasma discharges, there is a clear need to look at complementary techniques for the measurement of plasma current and magnetic parameters. Steady state magnetic sensors such as hall probes [1] and micromechanical magnetometers [2] are also considered as backup systems but they are active semiconductor devices using electronics exposed close to the harsh ITER environment making their operation questionable in the long term. An attractive alternative consists in using a fully passive fiber optic current sensor (FOCS). Its principle of operation is based on the Faraday rotation experienced by a polarized light beam passing through a fiber optic when the magnetic field is aligned with the fiber axis [3]. Fibers are