Optical Fiber Sensor Vibration Positioning via Stokes Vector Angular Velocity
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Solution Overview
Problem
Existing optical fiber sensor devices struggle to accurately detect and specify vibration-induced birefringence changes in optical fibers due to dependence on the polarization state of the input light wave, leading to inconsistent results and potential false detections or overlooking of abnormal vibrations.
Innovation Solution
An optical fiber sensor device that generates a polarization switched light beam and calculates an angular velocity vector to specify the fluctuation position of birefringence, independent of the polarization state of the input light wave, by observing the temporal changes in the Stokes vector of light waves propagating clockwise and counterclockwise through a loop-state optical fiber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the polarization state of the input light wave is used to detect birefringence changes, then the detection method is simple, but the detection results become inconsistent and unreliable due to dependence on random polarization states
Solution Approach 1:
The patent changes the parameter being measured from the polarization state of the output light (which depends on input polarization) to the angular velocity vector of the Stokes vector (which is independent of input polarization). This parameter transformation eliminates the reliability issue while maintaining detection simplicity.
Solution Approach 2:
The patent introduces the angular velocity vector as an intermediary quantity that mediates between the raw polarization state measurements and the final birefringence change detection. This intermediary eliminates the direct dependence on input polarization state while preserving the detection capability.
2Ease of operation
If the temporal change of polarization state is observed to detect vibration, then the detection principle is straightforward, but false detections or overlooked abnormal vibrations occur due to polarization state dependence
Solution Approach 1:
The patent transforms the measurement parameter from temporal change of polarization state (prone to false detections) to temporal change of angular velocity vector (robust against false detections). This maintains the straightforward detection principle while improving measurement precision.
3Device complexity
If light wave propagation time is used to specify vibration position, then the positioning method is simple, but accurate positioning becomes difficult when temporal changes of polarization states for clockwise and counterclockwise lights are different
Solution Approach 1:
The patent changes the comparison parameter from temporal changes of polarization states (which can be different for clockwise and counterclockwise lights) to temporal changes of angular velocity vectors (which are identical for both directions). This maintains the simple positioning method while ensuring accurate vibration position specification.
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
This approach allows for reliable and reproducible detection of birefringence changes in optical fibers, eliminating the reliance on input light polarization and improving the accuracy of vibration position specification.
Implementation Method 1
a temporal change of birefringence of the optical fiber involved in the vibration (a variation both of the phase difference generated between the birefringent axis and of the birefringent axis)
Implementation Method 2
a polarization state of a light wave output from the optical fiber is temporally changed
Implementation Method 3
the polarization states of respective light waves which have propagated clockwise and counterclockwise through the loop-state optical fiber are observed
Data Source
AI summary
The optical fiber sensor device comprises a probe light supply unit, an optical fiber sensor unit, and a polarization state measuring unit. The probe light supply unit generates and outputs a polarization switched light beam by alternately switching a polarized CW light beam in polarization directions orthogonal to each other with elapse of time. The optical fiber sensor unit includes a loop-state optical fiber into which the polarization switched light beam is input and which outputs a light wave reflecting a change of birefringence according to a stress applied from an outside in the polarization switched light beam. The polarization state measuring unit observes polarization states of the respective light waves propagating clockwise and counterclockwise through the optical fiber. The polarization state measuring unit calculates an angular velocity vector ωb defined by an equation that specifies a relationship between a temporal change rate dsout(t)/dt of a Stokes vector sout(t) giving a polarization state of the light wave from the optical fiber and the Stokes vector sout(t) for each of the clockwise and counterclockwise light waves. The angular velocity vector ωb gives a direction of a rotation center axis and a rotation angular velocity of the Stokes vector sout(t).