Dual-cladding fiber strain temperature measurement
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Solution Overview
Problem
Distributed strain sensing devices face cross-sensitivity issues due to simultaneous temperature and strain changes causing Rayleigh scattering spectral shifts, making it difficult to achieve precise measurements in applications like structural health monitoring.
Innovation Solution
The use of two optical fibers with different cladding diameters arranged in parallel, where the temperature and strain coefficients are distinct, allowing for matrix operation to separate and measure temperature and strain changes, thereby eliminating cross-sensitivity in optical frequency domain reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single mode fiber is used for distributed strain sensing based on Rayleigh scattering spectral shift, then high precision and high spatial resolution can be achieved, but cross sensitivity to temperature changes occurs making it difficult to distinguish strain from temperature effects
Solution Approach 1:
The sensing system is segmented into two parallel optical fibers with different cladding diameters. Each fiber provides an independent measurement channel with distinct temperature and strain sensitivity characteristics. By segmenting the sensing function across multiple fibers with different properties, the system can independently measure both temperature and strain without cross-sensitivity interference.
Solution Approach 2:
The invention changes the physical parameter of the optical fibers by using two fibers with different cladding diameters. This parameter change results in different temperature coefficients and strain coefficients for each fiber. By selecting fibers with appropriately different parameters, the system creates a measurable difference in spectral shifts that allows mathematical separation of temperature and strain effects through matrix operations.
2Measurement precision
If two optical fibers with different cladding diameters are used to eliminate cross sensitivity, then simultaneous temperature and strain measurement can be achieved, but device complexity increases
Solution Approach 1:
The invention merges two optical fibers with different cladding diameters into a single integrated sensing system. Both fibers are coupled with the same tunable laser source and their spectral shifts are measured using a unified optical frequency domain reflection system. The merging of multiple sensing functions into one system allows simultaneous measurement of temperature and strain while sharing common components, thereby managing complexity.
Solution Approach 2:
The optical frequency domain reflection system is designed with multi-functionality to handle both temperature sensing and strain sensing through the same hardware platform. The system can process signals from multiple fibers with different characteristics using a universal measurement approach, eliminating the need for separate dedicated systems for each measurement type.
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 enables simultaneous and precise measurement of strain and temperature changes by using standard and small-diameter optical fibers, reducing measurement errors and achieving effective cross-sensitivity elimination.
Implementation Method 1
a tunable laser providing a light source for the device so as to achieve linear scanning
Implementation Method 2
perform a distributed strain and temperature measurement based on Rayleigh scattering spectral shift of a single mode fiber in optical frequency domain reflection
Implementation Method 3
the 50:50 coupler is used for optical interference; the two emitted light beams are reflected by the first Faraday mirror and the second Faraday mirror for interference in the 50:50 coupler
Implementation Method 4
the two emitted light beams are reflected by the first Faraday mirror and the second Faraday mirror which are arranged at the arms of the light source phase monitoring system
Data Source
AI summary
The present invention discloses a distributed device for simultaneously measuring strain and temperature based on optical frequency domain reflection, comprising a tunable laser, a 1:99 beam splitter, a main interferometer system, a light source phase monitoring system based on an auxiliary interferometer, an acquisition device and a computer processing unit, wherein the main interferometer system comprises two Mach-Zehnder interferometers, and two optical fibers having different cladding diameters are arranged in parallel as sensing fibers. Due to the difference in temperature and strain coefficients of optical fibers of the same diameter, the temperature and strain values during changing the temperature and strain simultaneously can be obtained by matrix operation, thereby achieving an effect of eliminating cross sensitivity of temperature and strain sensing in optical frequency domain reflection.