Multicore Optical Fiber Strain Temperature Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing shape sensing systems using multicore optical fibers struggle to accurately distinguish between temperature changes and axial strain, as they do not provide a linearly independent measurement for temperature, leading to non-linear errors in determining the 3-D shape and position of the fiber.
Innovation Solution
Incorporating additional cores with a different thermal response into the multicore fiber, such as those doped with boron and germanium, which have a distinct temperature dependence of the index of refraction, allowing for linearly-independent temperature measurements and compensating for non-linear errors through interferometric detection and data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple distributed strain measurements are combined through a system of equations to produce physical measurements including curvature, twist, and axial strain, then the distributed shape and position of the optical fiber can be determined, but temperature changes cannot be distinguished from axial strain changes
Solution Approach 1:
The fiber is segmented into multiple cores with different thermal responses. By dividing the measurement function across cores with distinct thermal characteristics, the system can separately identify temperature and strain effects that would be indistinguishable in a single-core or uniformly-doped multicore fiber.
Solution Approach 2:
Different cores are doped with different materials (e.g., germanium vs. boron) to create local variations in thermal response. This local quality differentiation allows each core to respond uniquely to temperature changes, enabling the system to disentangle temperature and strain measurements through comparative analysis.
2Quantity of substance
If a fifth core is added to the multicore fiber to provide a separate fifth measurement, then more measurements are available, but the measurement is not linearly independent from the other four measurements
Solution Approach 1:
The fifth core is doped with different materials (e.g., boron and germanium) compared to the first four cores (e.g., germanium only), creating a distinct local quality in terms of thermal response. This differential doping ensures that the fifth core's measurement is linearly independent from the other cores, as it responds differently to temperature changes.
3Measurement precision
If additional cores with different thermal response are incorporated into the multicore fiber, then linearly-independent temperature measurements can be obtained, but the device complexity increases
Solution Approach 1:
The thermal response parameter of the fiber cores is changed by varying the dopant composition. By adjusting the dopant types and concentrations during manufacturing, cores with distinct thermal characteristics are created without fundamentally changing the overall fiber structure or requiring additional complex components.
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 enhances the accuracy of shape sensing by providing a separate, independent measurement for temperature, enabling precise determination of axial strain, bend strain, twist strain, and temperature, thereby improving the system's ability to calculate the 3-D shape and position of the optical fiber.
Implementation Method 1
an interferometric measurement system comprising: interferometric detection circuitry configured to detect measurement interferometric pattern data associated with each of the multiple first cores and each of the one or more second cores
Implementation Method 2
a multicore optical fiber having first and second optical cores adapted to transmit optical signals having first and second predetermined wavelengths, respectively, in a single spatial mode
Implementation Method 3
The first and second optical cores each include a respective Bragg grating adapted to reflect optical signals having the first and second predetermined wavelengths, respectively
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An optical fiber includes multiple optical waveguides configured in the fiber. An interferometric measurement system mitigates or compensates for the errors imposed by differences in a shape sensing optical fiber's response to temperature and strain. A 3-D shape and/or position are calculated from a set of distributed strain measurements acquired for a multi-core optical shape sensing fiber that compensates for these non-linear errors using one or more additional cores in the multicore fiber that react differently to temperature changes than the existing cores.