Fiber Bragg Grating Overheat Detection Calibration
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Solution Overview
Problem
Existing aircraft overheat detection systems based on eutectic salt technology provide only binary indications of overheat events, lacking precision in temperature monitoring and location identification, which is insufficient for modern aircraft requirements, especially with the increased sensitivity of composite materials to temperature changes.
Innovation Solution
A fiber optic overheat detection system using fiber Bragg gratings (FBGs) that transmit optical signals through aircraft zones, allowing for continuous temperature and strain monitoring, enabling precise temperature profiling and location identification of overheat events, and integrating calibration FBGs for accurate temperature sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If eutectic salt technology is used for overheat detection, then the system can detect overheat events, but it only provides binary indications without precise temperature monitoring or location identification
Solution Approach 1:
The optical fiber is divided into multiple discrete Fiber Bragg Gratings (FBGs) at different locations along the fiber. Each FBG acts as an independent sensing element that reflects a specific wavelength, enabling both precise temperature measurement and location identification of overheat events along the aircraft structure.
Solution Approach 2:
The system transitions from binary detection (overheat/not overheat) to continuous multi-dimensional monitoring by using wavelength division multiplexing. Each FBG reflects a unique wavelength corresponding to its position, adding a spatial dimension to the temperature detection capability.
2Measurement precision
If Fiber Bragg Gratings are used for continuous temperature monitoring, then precise temperature profiling is achieved, but system complexity increases due to multiple FBGs and calibration requirements
Solution Approach 1:
The system incorporates self-calibration functionality where reference FBGs with known characteristics are used to automatically calibrate the temperature measurements of sensing FBGs. The interrogator device performs automated calibration routines using these reference elements, eliminating the need for manual calibration and reducing operational complexity.
Solution Approach 2:
Reference FBGs are pre-installed at known locations along the optical fiber during manufacturing. These reference elements are positioned at specific intervals and have predetermined characteristics that enable the system to perform self-calibration without requiring external intervention or complex setup procedures.
3Loss of information
If multiple FBGs are installed along the optical fiber for distributed sensing, then location identification improves, but the difficulty of detecting and measuring individual FBG signals increases
Solution Approach 1:
The system uses wavelength division multiplexing to differentiate between multiple FBGs. Each FBG is designed to reflect a unique wavelength within the optical spectrum, allowing the interrogator to identify both the location and temperature of each FBG by detecting its specific reflected wavelength, thus simplifying the detection of multiple sensors.
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 system provides detailed temperature and strain trend data, enabling preventative maintenance and reducing downtime by accurately detecting overheat events and their locations, thus enhancing aircraft safety and efficiency.
Implementation Method 1
overheat fiber Bragg gratings... configured to reflect an optical signal
Data Source
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AI summary
A system configured to monitor a plurality of zones of an aircraft includes a line replaceable unit, a first interrogator, and a controller. The line replaceable unit includes first and second connectors in optical communication and an optical fiber. The optical fibers includes a first plurality of fiber Bragg gratings and a plurality of calibration fiber Bragg gratings in a pattern providing information related to a calibration value based upon a center wavelength of each of the first plurality of fiber Bragg gratings. The first interrogator is connected to the line replaceable unit at the first end of the optical fiber and is configured to provide a first optical signal and to receive a first optical response signal from the optical fiber. The controller is operatively connected to the first interrogator and is configured to determine the calibration value of the line replaceable unit.