Faraday rotation in coiled, monomode optical fibers: isolators, filters, and magnetic sensors

Abstract

It is shown that efficient Faraday rotation can be obtained in a fiber coil if the circumference of the coil is exactly equal to the beat length of the birefringence caused by bending. The essential elements of a practical, compact isolator based on this principle are demonstrated. Forty-five degrees of Faraday rotation were obtained in a 40-turn, 15-mm-diameter coil placed in the field of a permanent magnet (~0.29 T). The design of optical filters and magnetic sensors is also discussed.