FBG Sensor Embedded in Composite Substrate for Wide Temperature Sensitivity
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Solution Overview
Problem
Existing optical fiber temperature sensors face challenges in maintaining sensitivity in extremely low temperature regions and are prone to damage due to exposure, limiting their applicability in wide temperature ranges and harsh environments like space.
Innovation Solution
The optical fiber temperature sensor employs a substrate with a first and second substrate main body, where the second substrate has a higher coefficient of thermal expansion, bonded to the first, embedding the FBG sensor portion within the second substrate to apply compressive or tensile strains, enhancing sensitivity and protection from external impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the FBG sensor portion is embedded in a substrate made of CFRP, then the sensor is protected from external damage, but the sensitivity of the sensor reduces in the extremely low temperature region of -50°C or less
Solution Approach 1:
The patent uses a composite substrate structure consisting of a CFRP base layer and a separate thermal expansion compensation layer. This composite structure allows the sensor to benefit from both the mechanical protection of CFRP and the thermal sensitivity enhancement from the compensation layer, resolving the contradiction between protection and sensitivity in extreme temperatures
Solution Approach 2:
The patent changes the thermal expansion parameters of the substrate by introducing a layer with specific thermal expansion characteristics. This parameter modification enables the substrate to compensate for thermal effects in extreme temperatures, maintaining sensor sensitivity while preserving the protective function
2Measurement precision
If the FBG sensor portion is bonded onto a bimetal, then the sensor can measure temperature through strain conversion, but the measurement range is limited to a narrow temperature region of -20°C to 40°C
Solution Approach 1:
The patent utilizes thermal expansion principles by designing a substrate with specific thermal expansion characteristics that can accommodate and amplify thermal effects across a wide temperature range. This allows the FBG sensor to maintain sensitivity and measurement capability from -170°C to 150°C, overcoming the limited range of bimetal-based sensors
3Device complexity
If the FBG sensor portion is left in an exposed state, then the sensor structure is simple, but the sensor is liable to be damaged by impact or rubbing during assembly and conveyance
Solution Approach 1:
The patent embeds the FBG sensor portion within the substrate structure, nesting the sensitive sensor element within a protective matrix. This nesting approach provides mechanical protection against impact and rubbing during handling and conveyance, while the integrated design does not significantly increase overall device complexity
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 configuration improves sensor sensitivity across a wide temperature range, from -170°C to 150°C, while protecting the FBG sensor from damage, enabling high-accuracy multipoint temperature measurements.
Implementation Method 1
a second substrate main body 32 having a coefficient of thermal expansion larger than that of the first substrate main body 31
Implementation Method 2
a fiber Bragg grating (FBG) in which the Bragg wavelength of a reflectance spectrum changes with a temperature and a strain
Data Source
AI summary
An optical fiber temperature sensor includes: a substrate having a first substrate main body, and a second substrate main body, which has a coefficient of thermal expansion larger than that of the first substrate main body, and is bonded to the first substrate main body; and an optical fiber having a FBG sensor portion for measuring a temperature from a relationship between a Bragg wavelength and the temperature, and the optical fiber is configured to be embedded in the second substrate main body so that the FBG sensor portion is positioned in the second substrate main body.