Fiber optic magnetic field sensing system based on lorentz force method for downhole applications

摘要: A method and apparatus for magnetic sensing is described. The includes a strain-sensing fiber coupled to conducting strip. may be, example, distributed feedback with Bragg gratings. current be induced flow on the strip by electrically coupling photodiode then activating laser optically photodiode. In presence of field, Lorentz force will exerted strip, causing displacement that induce strain fiber. measured laser-pumping measuring reflected waves. used calculate magnitude field. Multiple fibers in series deployed into borehole field measurements. measurements determine resistivity formations surrounding and, monitor movement relatively-low water fronts.