Optical detection of magnetic field inhomogeneities

A small piece of glass-coated amorphous Fe₇₆Si₉B₁₀P₅ microwire is attached to the surface of the optical fiber at its end. At approximately 250 micrometers from the end of the optical fiber containing the microwire, a reflective surface is placed, and an optical signal from a broad-spectrum SLED source with a central wavelength of 1480nm is introduced into the fiber. Using an optical fiber circulator and an optical spectrum analyzer, we monitor the interference in the spectral region of optical signals reflected from the end of the fiber and the reflecting surface behind the end of the fiber. By applying a transverse static magnetic field to the end of the fiber with a microwire, we change the lateral position of the optical fiber. As a result, we observe the spectral shift of the interference pattern due to the change in the optical path between the interfering optical signals. The spectral shift as a function of magnet distance d_m from the optical fiber with the microwire is measured, which represents the potential for finding applications allowing to investigate or measure magnetic fields or gradients, or small changes in the distance between two objects in a non-contact manner.