Pi-Phase Shifted Fiber Bragg Grating Strain Sensor
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Solution Overview
Problem
Existing optical strain sensors, despite their advantages over electrical sensors, face limitations in resolution and are not optimized for high-precision strain measurements in harsh environments.
Innovation Solution
The development of an optical sensing system incorporating a π-phase-shifted fiber Bragg grating inscribed on a sensing optical fiber, which is attached to a deformable member within a frame, allowing for increased resolution and robust strain measurements by monitoring the Bragg wavelength shift, and a signal conditioner to generate signals representative of these shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Fiber Bragg Gratings are used for strain sensing, then the sensor can measure strain and temperature, but the resolution is insufficient for high-precision measurements
Solution Approach 1:
The patent introduces a π-phase-shift defect at the center of the FBG, creating a localized region with different refractive index properties. This local modification creates a sharp resonance peak that significantly enhances the sensitivity to strain and temperature changes, thereby improving measurement resolution without compromising reliability in harsh environments
Solution Approach 2:
The patent modifies the physical parameters of the FBG by introducing a phase shift that changes the refractive index distribution along the fiber. This parameter change transforms the grating's spectral characteristics, producing a narrow resonance peak that enables high-resolution measurements while maintaining stability under varying environmental conditions
2Adaptability or versatility
If standard FBGs are used in harsh environments, then the sensor can operate in high temperature and radiation areas, but the measurement resolution deteriorates
Solution Approach 1:
By introducing a localized π-phase-shift defect in the FBG structure, the patent creates a specific region with enhanced sensitivity characteristics. This local modification produces a sharp resonance peak that maintains high measurement resolution even when the sensor operates in harsh environments with high temperatures and radiation
Solution Approach 2:
The patent designs the FBG with a pre-engineered π-phase-shift defect that anticipates and compensates for the degradation of measurement resolution in harsh environments. This beforehand optimization ensures that the sensor maintains high precision across a wide operational range without requiring additional protection or calibration
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 solution enhances the resolution of strain measurements by a factor of 100, enabling sub-nano-strain changes to be monitored, and allows the system to operate across a wide temperature range while maintaining accuracy in force measurement applications.
Implementation Method 1
FBGs can be used as wavelength selectable mirrors, where some wavelengths of light are reflected, while some other wavelengths of light are allowed to pass through. The periodic pattern includes variations of the refractive index of the core of the optical fiber, which can act as reflective interfaces for at least some wavelengths, generally referred to as the Bragg wavelength λB.
Implementation Method 2
at least one π-phase-shifted fiber Bragg grating inscribed thereon, the at least one π-phase-shifted fiber Bragg grating of the sensing optical fiber deforming together with the deformable member when the frame is subjected to a force
Implementation Method 3
applying a strain to an optical fiber having a FBG inscribed in its core will modify the length of the optical fiber which will, in turn, change the pitch the Bragg wavelength λB of its FBG. This change can be monitored, enabling strain measurements to be performed optically
Data Source
AI summary
The optical sensor generally has a frame having a deformable member mounted to the frame, and a sensing optical fiber being fixedly attached to a portion of the deformable member, the sensing optical fiber having at least one π-phase-shifted fiber Bragg grating inscribed thereon, the at least one π-phase-shifted fiber Bragg grating of the sensing optical fiber deforming together with the deformable member when the frame is subjected to a force.