Optical Fiber Birefringence Compensation Mirror for Current Sensors
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Solution Overview
Problem
Current current sensors using optical fibers face challenges with birefringence-induced measurement errors due to external vibrations and temperature changes, particularly when using quartz-based fibers, which affect the accuracy of large-magnitude current detection and require complex alignment procedures for polarization plane rotation mirrors.
Innovation Solution
An optical fiber birefringence compensation mirror is introduced, comprising a single-mode optical fiber, a birefringent element, a Faraday rotator, and a mirror, where the components are arranged to divide the light beam into perpendicular polarized beams that are reflected in point symmetry, compensating for birefringence and improving vibration resistance by ensuring optimal coupling positions and preserving polarization plane perpendicularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polarization plane rotation mirror is used to compensate for birefringence, then measurement accuracy is improved, but alignment complexity increases due to difficulty in determining optimal coupling positions
Solution Approach 1:
A λ/4 plate is introduced as an intermediary component between the optical fiber and the mirror. This plate transforms the polarization state of light in a controlled manner, enabling the system to compensate for birefringence effects without requiring complex alignment procedures. The λ/4 plate acts as a mediator that simplifies the coupling process while maintaining measurement accuracy.
Solution Approach 2:
The invention changes the polarization parameters of light by using a λ/4 plate to convert linearly polarized light into circularly polarized light before reflection, and then back to linearly polarized light with a 90-degree rotation. This parameter transformation approach allows for effective birefringence compensation while avoiding the alignment complexity associated with direct polarization plane rotation mirrors.
2Quantity of substance
If quartz-based optical fibers are used for current detection, then large-magnitude current detection capability is improved, but measurement accuracy deteriorates due to birefringence-induced errors from external vibrations and temperature changes
Solution Approach 1:
The invention converts the harmful birefringence effect into a beneficial compensation mechanism. By introducing a λ/4 plate and configuring the optical path with a mirror, the system deliberately induces controlled polarization changes that counteract the unwanted birefringence effects from external vibrations and temperature variations. This transforms the problematic birefringence phenomenon into a useful compensation tool that maintains measurement accuracy while preserving the ability to detect large-magnitude currents.
3Reliability
If lead oxide-containing optical fibers are used to reduce birefringence, then vibration resistance is improved, but current detection capability is reduced
Solution Approach 1:
Instead of changing the fiber material parameters (as would be required to use lead oxide-containing fibers), the invention changes the optical path parameters by introducing a λ/4 plate and configuring a specific optical arrangement with a mirror. This parameter transformation approach achieves vibration resistance through controlled polarization management without sacrificing current detection capability, allowing the use of standard quartz-based fibers that maintain high detection performance.
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 solution effectively compensates for birefringence in optical fibers, enhancing vibration resistance and allowing the use of quartz-based fibers for detecting large-magnitude currents with improved temperature stability and simplified alignment, reducing measurement errors and changing the ratio error-temperature characteristics.
Implementation Method 1
a light beam propagating through the optical fibre is divided into two perpendicular linearly polarized light beams of an ordinary ray, or beam and an extraordinary ray, or beam by the birefringent element
Implementation Method 2
a Faraday rotator which is applied with a magnetic field from the magnet to be magnetically saturated and has a Faraday rotation angle of 45 degrees; the two linearly polarized light beams transmit through the Faraday rotator, therefore polarization planes thereof are rotated by 45 degrees
Implementation Method 3
the two linearly polarized light beams are reflected at one point on a surface of the mirror in point symmetry
Implementation Method 4
a lens; the light beam propagating through the optical fibre is divided into two perpendicular linearly polarized light beams... to be condensed by the lens
Data Source
Figure 1~2
Figure 3(A)~3(F)
Figure 4~5
AI summary
Disclosed is an optical fibre birefringence compensation mirror which as well as being easy to align and assemble, compensates for the birefringence generated by a sensor optical fibre, particularly in current sensors, increases the vibration resistance of a current sensor, and enables large current detection by a current sensor. Also disclosed is a current sensor wherein vibration resistance has been increased due to the optical connection of the optical fibre birefringence compensation mirror. The optical fibre birefringence compensation mirror comprises: an optical fibre, a birefringence element, a lens, a magnet, a Faraday rotator, and a mirror. From the light incidence/emission end surface of the optical fibre, the birefringence element, Faraday rotator, and mirror are arranged in said order, and the optical fibre is a single mode type optical fibre. Light comes in from the optical fibre, and is separated into two linearly polarised lights by the birefringence element. The polarisation planes of the two linearly polarised lights are rotated by 45 degrees by the Faraday rotator, and the two linearly polarised lights are point-symmetrically reflected at one point by the mirror, then once again rotated by 45 degrees by the Faraday rotator, then re-combined to be one light by the birefringence element and made to enter the optical fibre.