Proposal for detection of magnetic fields through magnetostrictive perturbation of optical fibers.

We analyze the possibility of detecting weak magnetic fields by using magnetostrictive perturbation of optical fibers. The basic scheme is demonstrated in Fig. 1. A low-loss optical fiber of length L is sheathed in a magnetostrictive jacket that undergoes a longitudinal strain (magnetostriction) when immersed in a magnetic field. This strain affects the phase delay of a laser light beam propagating in the fiber. Experimental data of the longitudinal strain ce induced by a magnetic field H are shown in Fig. 2, reproduced from Ref. 1. Using this figure, we can approximate the data for nickel by