Development of a Multimaterial Optical Fiber for Fully Distributed Magnetic Sensing Applications

A novel multimaterial fiber optic magnetic sensing design is presented and evaluated in this letter. The multimaterial optical fiber has demonstrated
$ < 0.2\ n\epsilon $
sensitivity to external magnetic fields over a 2-m gauge length. Intended for immediate use in unconventional oil and gas (UOG) and measuring while drilling (MWD), this instrument could have wide-ranging subsurface sensing applications. Composed of fused silica cladding, internally distributed ferromagnetic nickel, and a series of fiber Bragg gratings, the multimaterial structure has been consistently drawn to over 1 km of length on a fiber draw tower. Due to the consistency of manufacturability and high magnetic sensitivities over long lengths, the proposed design may be considered a competitive magnetic sensor in UOG and MWD applications.