Optical Shape Sensing Stability Module for Fiber Optics
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Solution Overview
Problem
Optical shape sensing systems using fiber optics often become unstable due to factors like loss of laser alignment, phase tracking failure, motion near the launch region, improper calibration, temperature variations, local pressure/stress, high twist/roll, and axial tension, leading to incorrect shape reconstructions.
Innovation Solution
A stability module is implemented in the system to detect and correct erroneous shape data by employing parameters such as nodal position, twist, and spatio-temporal continuity, rejecting data that exceeds acceptable thresholds and replacing it with reliable data to ensure accurate shape sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical shape sensing is performed using fiber optics with distributed strain measurement, then shape and position data can be obtained, but the system becomes unstable due to temperature variations, strain effects, and environmental factors causing wavelength shift and measurement errors
Solution Approach 1:
The patent introduces a stability module as an intermediary component that processes raw shape sensing data and filters out unstable measurements. This module acts as a mediator between the optical fiber sensing system and the final shape reconstruction, eliminating incorrect shape data caused by temperature and strain variations while preserving accurate measurements.
Solution Approach 2:
The system implements feedback mechanisms through laser realignment and recalibration procedures. When instability is detected in the shape sensing data, the system automatically performs realignment of the optical system and recalibration of polarization states, creating a closed-loop control system that maintains measurement stability despite environmental variations.
2Measurement precision
If laser realignment and calibration are performed frequently to maintain accuracy, then measurement precision improves, but system complexity and operation time increase
Solution Approach 1:
The patent performs laser realignment and calibration procedures in advance, before actual shape sensing measurements are taken. By establishing proper polarization states and optical alignment beforehand, the system reduces the need for frequent realignment during operation, thereby maintaining measurement precision while minimizing operational complexity.
Solution Approach 2:
The stability module automatically detects and corrects unstable data without requiring manual intervention. The system self-adjusts by identifying incorrect shape measurements and filtering them out, reducing the operational burden on users while maintaining high measurement precision.
3Device complexity
If the optical system is kept simple without stability correction, then device complexity is reduced, but measurement reliability and stability deteriorate
Solution Approach 1:
The patent divides the shape sensing system into separate functional modules: the optical fiber sensing section, the stability module for data filtering, and the shape reconstruction section. This segmentation allows the stability correction functionality to be added as a distinct module without fundamentally redesigning the entire optical system, thus maintaining relative simplicity while improving reliability.
4Measurement precision
If axial strain is applied to the fiber for shape measurement, then shape data can be obtained, but wavelength shift occurs due to strain-optic effects, reducing measurement accuracy
Solution Approach 1:
The patent compensates for wavelength shift caused by axial strain by introducing counteracting strain through the coating layer or surrounding structure. This parameter change approach modifies the strain distribution around the fiber core to offset the wavelength shift, thereby maintaining measurement accuracy without sacrificing shape measurement capability.
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 enhances the stability and accuracy of shape sensing by eliminating incorrect shapes and improving performance, even in dynamic environments like cardiac interventions, by providing a stable shape sensing data set.
Implementation Method 1
Shape sensing based on fiber optics exploits the inherent backscatter in a conventional optical fiber. The principle involved makes use of distributed strain measurement in the optical fiber using characteristic Rayleigh backscatter patterns.
Implementation Method 2
The temperature coefficient K T is a sum of the thermal expansion coefficient α = (1 /A)(∂A/∂T) and the thermo-optic coefficient
Implementation Method 3
The temperature coefficient K T is a sum of the thermal expansion coefficient α = (1 /A)(∂A/∂T) and the thermo-optic coefficient, ξ = (1 /n)(∂n/ ∂T)
Implementation Method 4
Kε is a function of group index n, the components of the strain-optic tensor, p ij and Poisson's ratio, μ
Data Source
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AI summary
A system and method for shape sensing with optical fiber include collecting (610) shape data from a shape sensing optical fiber device. The shape data are tested (620) to determine data positions that exceed an acceptable threshold based on geometrical expectations of the shape data. The shape data corresponding to the data positions that exceed an acceptable threshold are rejected(640). Acceptable shape data are rendered (650) to provide a stable shape sensing data set.