Fiber Optic Temperature Sensors in Inert Gas for Cryogenic Environments
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Solution Overview
Problem
Current temperature measurement methods in cryogenic environments face challenges such as limited resolution and increased complexity with the number of sensors, and optical fiber-based systems experience mechanical strain issues due to air and moisture adhesion at cryogenic temperatures.
Innovation Solution
A fiber optic temperature sensor system using optical fibers with multiple Fiber Bragg gratings, encased in sealed tubing filled with an inert gas, which removes moisture from the fiber coating and prevents air and moisture adhesion, allowing for high-resolution, distributed temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical fibers are used for temperature sensing in cryogenic environments, then high-resolution distributed temperature measurements are achieved, but mechanical strain occurs due to frozen adhesion of air and moisture to the fiber at cryogenic temperatures
Solution Approach 1:
The patent applies the inert atmosphere principle by evacuating air and moisture from the protective tubing and replacing it with an inert gas (such as nitrogen or helium) that remains gaseous at cryogenic temperatures. This prevents the frozen adhesion that would otherwise occur with air and moisture, eliminating the mechanical strain on the optical fiber while maintaining high-resolution temperature measurements throughout the cryogenic environment
2Quantity of substance
If multiple diodes are mounted on a ribbon to achieve distributed temperature sensing, then temperature readings across the cryogenic environment are obtained, but the system becomes more complex and difficult to install and maintain
Solution Approach 1:
The patent merges multiple temperature sensing functions into a single optical fiber by incorporating multiple Fiber Bragg grating sensors along the length of one fiber. This allows distributed temperature measurements at multiple locations to be achieved through one fiber rather than requiring multiple separate diode sensors, significantly reducing system complexity while maintaining the ability to monitor temperatures across the entire cryogenic environment
Solution Approach 2:
The patent replaces the electrical diode-based measurement system with an optical fiber-based system using Fiber Bragg gratings. This substitution eliminates the need for associated wiring and electrical connections for each sensor point, reducing installation and maintenance complexity while enabling distributed temperature sensing along the fiber length
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
Enables high-resolution, easy-to-install and maintain temperature sensing across large cryogenic environments by preventing mechanical strain and ensuring accurate readings through the use of inert gas-filled protective tubing and a fiber optic interrogation system.
Implementation Method 1
employing this method in cryogenic environments is problematic. The optical fibers would require mechanical protection in such environments (such as PTFE tubing). However, both air and moisture may cause frozen adhesion of an optical fiber to PTFE tube walls at cryogenic temperatures. These adhesions produce unwanted strains induced into the fiber temperature measurement.
Implementation Method 2
The tubing is filled with an inert gas and a fiber optic interrogation system attached to the free end of the optical fiber to obtain temperature readings when the device is deployed in a cryogenic environment.
Data Source
AI summary
The present invention is a temperature sensor for cryogenic systems using a fiber optic interrogation system that is capable of a large number of temperature readings across the cryogenic environment at high resolutions. The invention also includes a method of using such a system to measure temperatures in a cryogenic environment and a method of making such a system.