Gadolinium-Doped Fiber Magnetic Field Sensor
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Solution Overview
Problem
Current magnetic field sensors using optical fibers are bulky and expensive due to the need for long silica fibers to achieve sufficient sensitivity, and high-dopant fibers like terbium-doped fibers are difficult to handle and integrate into sensors effectively.
Innovation Solution
A magnetically responsive light propagating component doped with gadolinium at a low concentration, which provides a high Verdet constant, allowing for a compact and cost-effective fiber-based magnetic field sensor that can rotate the polarization of light in response to a magnetic field, thus enabling efficient magnetic field detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If normal silica fibers are used to achieve sufficient Faraday rotation, then the magnetic field sensitivity is improved, but the fiber length required increases resulting in a bulky sensor system
Solution Approach 1:
The patent changes the material composition parameter by doping silica fiber with gadolinium ions, which fundamentally alters the Verdet constant from a marginal value to a high value, enabling sufficient Faraday rotation in a compact fiber length
Solution Approach 2:
The patent creates a composite material system combining silica fiber with gadolinium dopant, leveraging the magneto-optic properties of gadolinium to enhance the Faraday rotation effect while maintaining the optical waveguide properties of silica
2Measurement precision
If high concentration terbium dopant is used to increase Faraday rotation, then the Verdet constant is improved, but the fiber becomes difficult to handle and splice with significantly different softening point
Solution Approach 1:
The patent optimizes the dopant concentration parameter to a low level (0.01-5 wt%) which provides sufficient Verdet constant enhancement while maintaining the fiber's softening point and mechanical properties close to conventional silica, enabling easy handling and splicing
Solution Approach 2:
The patent selects gadolinium as the dopant material which is more abundant and easier to work with compared to terbium, reducing both material cost and processing complexity while achieving the desired magneto-optic performance
3Measurement precision
If high concentration terbium dopant is used to achieve high Verdet constant, then the Faraday rotation is improved, but the production cost increases significantly
Solution Approach 1:
The patent optimizes the dopant concentration to a low level (0.01-5 wt%) which reduces the amount of expensive rare-earth material required while still achieving sufficient Verdet constant enhancement for practical magnetic field sensing applications
Solution Approach 2:
The patent substitutes terbium with gadolinium, a more abundant and less expensive rare-earth element, thereby reducing material costs while maintaining the desired magneto-optic performance through optimized doping concentration
4Measurement precision
If high concentration terbium dopant is used to increase Faraday rotation, then the Verdet constant is improved, but the coupling and propagation losses increase making the fiber impractical
Solution Approach 1:
The patent optimizes the dopant concentration parameter to a low level (0.01-5 wt%) which minimizes scattering and absorption losses in the fiber while still providing sufficient Faraday rotation through the enhanced Verdet constant of gadolinium-doped silica
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 use of gadolinium-doped fibers results in a high Verdet constant, enabling a shorter, less complex magnetic field sensor with lower production and handling costs, and reduced propagation losses, allowing for sensitive and compact magnetic field sensing and distributed measurements over a wide area.
Implementation Method 1
a fiber that is configured to act as a Faraday rotator to rotate the polarization azimuth of linearly polarized light passing through it due to an applied magnetic field
Implementation Method 2
The magnetically responsive light propagating component is formed of a bulk material doped with a dopant, the dopant including at least gadolinium
Data Source
AI summary
A magnetic field sensor comprises a magnetically responsive light propagating component configured to cause a polarization of light propagating inside the component to be rotated in response to an applied magnetic field, wherein the magnetically responsive light propagating component is formed of a bulk material doped with a dopant, the dopant including at least gadolinium, the dopant concentration being at a sufficiently low concentration such that the dopant is uniformly dispersed in the bulk material to provide a high Verdet constant. The magnetic field sensor also comprises a detector, and a polarization-maintaining light input device to couple the light into the magnetically responsive light propagating component. The detector is configured to measure a property of light output from the magnetically responsive light propagating component to determine a change in polarization of the light, the change caused by the presence of a magnetic field.