RECIPROCAL AND QUASI-RECIPROCAL BRILLOUIN FIBEROPTIC CURRENT SENSORS

A novel current sensor based on the interaction between two counter-pr opagating Brillouin fiber-optic lasers has been investigated. Polariza tion problems specific to current sensors are addressed and are solved by means of a mechanically twisted fiber-ring resonator including a p olarization controller. The two proposed reciprocal and quasireciproca l configurations shows a linear response with a sensitivity of 126 Hz/ A that is very dose to the maximum sensitivity obtained by using fiber s without linear birefringence. The limitations of the reciprocal conf iguration due to the lock-in range, the Kerr effect induced by the pum p walk-off and by the pump intensity fluctuations are fully characteri zed. These limitations are compared with the limitations due to therma l drifts of the quasireciprocal configuration which alfows direct dete ction of the current direction.