Optical Fiber Magnetic Gradient Sensing via Ferromagnetic Suspension
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Solution Overview
Problem
Existing magnetometer arrays used for measuring magnetic fields are cumbersome and lack sensitivity and signal resolution, especially when hundreds of sensors are required, due to the need for magnetostrictive materials that detract from sensitivity and compactness.
Innovation Solution
A method and system using a multi-bay support structure with optical fibers and ferromagnetic members suspended in voids, where magnetic field gradients induce tension in the fibers, allowing for sensitive measurement of magnetic field gradients without attaching magnetostrictive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If magnetostrictive materials are attached to FBG for magnetic field detection, then magnetic field sensing capability is achieved, but sensitivity and signal resolution deteriorate
Solution Approach 1:
The invention extracts and removes the magnetostrictive material from the sensing system entirely. Instead of using magnetostrictive materials attached to FBG, the patent employs a magnetostrictive fluid that flows through a channel adjacent to the optical fiber, allowing magnetic field detection without the detrimental effects of attached magnetostrictive materials on sensitivity and signal resolution
Solution Approach 2:
The invention introduces a magnetostrictive fluid as an intermediary between the magnetic field source and the optical fiber. The fluid mediates the interaction by converting magnetic field variations into mechanical strain on the fiber through its flow characteristics, enabling indirect sensing that preserves optical fiber sensitivity
2Adaptability or versatility
If magnetostrictive materials are embedded or coated on fiber, then magnetic field detection is enabled, but device compactness and sensor density deteriorate
Solution Approach 1:
The invention extracts magnetostrictive materials from direct contact with the fiber and places them in a separate flow channel. This separation eliminates the bulk volume required for embedding or coating magnetostrictive materials, enabling compact sensor design with high sensor density
Solution Approach 2:
The invention uses a thin-walled flow channel structure that allows the optical fiber to remain exposed and flexible. The channel walls are thin enough to transmit magnetic field effects to the fiber while maintaining a compact overall structure, avoiding the bulkiness of traditional magnetostrictive coatings
3Adaptability or versatility
If magnetostrictive materials are attached to FBG, then magnetic field sensing is achieved, but sensor hysteresis and thermal sensitivity increase
Solution Approach 1:
The magnetostrictive fluid acts as an intermediary that decouples the magnetic field sensing function from the optical fiber. The fluid's flow-based mechanism avoids the hysteresis inherent in solid magnetostrictive materials, and the fluid's thermal properties can be optimized to reduce thermal sensitivity, improving overall sensor reliability
Solution Approach 2:
The invention replaces the mechanical attachment of solid magnetostrictive materials with a fluid-based system. The fluid dynamically responds to magnetic fields through flow rather than static mechanical deformation, eliminating hysteresis effects and reducing thermal sensitivity associated with solid material attachments
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides a lightweight, dense-array magnetometer with enhanced sensitivity and signal resolution, capable of measuring magnetic field gradients with high precision, suitable for multiplexed or branched fiber optic sensing networks.
Implementation Method 1
a magnetic member suspended in a void to strain an optical fiber, whereby when the magnetic member encounters a magnetic field gradient that induces forces producing displacement of the magnetic member which is then measurable as strain in the optical fiber
Implementation Method 2
When incorporated into an optical fiber, an FBG reflects particular wavelengths of light based on its Bragg wavelength, an inherent characteristic of the FBG for a given mode. Strain acting on the fiber and thus on the FBG will alter the reflected wavelength.
Data Source
AI summary
A system for measuring magnetic field gradients comprising a multi-bay support structure with a series of raised contact shoulders separated from each other by voids. An optical fiber is spaced along the length of the multi-cell support structure and traverses all the raised contact points and voids. The optical fiber has a plurality of Fiber Bragg gratings (FBGs) spaced lengthwise, each FBG suspended in a void. In addition, a plurality of ferromagnetic members are strung onto the optical fiber, each suspended in a void. Magnetic field gradients act on the ferromagnetic member to create localized tension in the optical fiber. The FBG's refractive indices are monitored, tension is calculated therefrom, and the tension is correlated to the magnetic field gradient. This greatly simplifies mechanical, optical, electronic and computational complexity and is bay suited for any FOSS array for measuring magnetic fields using many dense measurement points.