Optical Fiber Sensor Simultaneous Temperature Strain Measurement
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Solution Overview
Problem
Optical fiber sensor systems using FBG sensors and OFDR analysis struggle to simultaneously measure temperature and strain with high spatial resolution due to challenges in splitting measuring light into orthogonal polarization axes and maintaining consistent optical path-lengths, leading to inaccurate position identification and requiring separate temperature-compensating sensors.
Innovation Solution
A physical quantity measuring apparatus employing a tunable laser, polarization-maintaining fibers, a polarization-maintaining coupler, and an optical path-length adjuster, with incidence parts and optical path-length adjusters to ensure measuring light is split correctly and optical path-lengths are kept constant, allowing for simultaneous measurement of temperature and strain by analyzing wavelength changes in Bragg reflected lights from orthogonal polarization axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If measuring light is split into orthogonal polarization axes using conventional methods, then simultaneous measurement of temperature and strain becomes possible, but optical path-length inconsistency occurs leading to inaccurate position identification
Solution Approach 1:
A polarization-maintaining coupler is introduced as an intermediary device to split the measuring light into orthogonal polarization axes. This coupler ensures that the optical path-lengths of both polarization components are equalized, thereby maintaining accurate position identification while enabling simultaneous temperature and strain measurement through the FBG sensor.
2Measurement precision
If separate temperature-compensating sensors are used, then temperature and strain can be independently measured, but device complexity increases
Solution Approach 1:
The FBG sensor system is designed to perform multiple functions simultaneously. By utilizing the polarization-maintaining coupler to split light into orthogonal polarization axes, a single FBG sensor can independently measure both temperature and strain, eliminating the need for separate temperature-compensating sensors and reducing overall system complexity.
3Measurement precision
If high spatial resolution is achieved through OFDR analysis, then position identification precision improves, but the requirement for consistent optical path-lengths becomes more critical
Solution Approach 1:
The polarization-maintaining coupler serves as a critical intermediary that automatically equalizes optical path-lengths for orthogonal polarization components. This design feature becomes increasingly important when achieving high spatial resolution through OFDR analysis, as it ensures that the consistent optical path-length requirement is met without adding complex external control mechanisms.
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 accurate simultaneous measurement of temperature and strain with high spatial resolution, eliminating the need for separate temperature-compensating sensors and ensuring precise identification of sensor positions, thereby enhancing the capability for structural health monitoring.
Implementation Method 1
a tunable laser that emits measuring light
Implementation Method 2
a polarization-maintaining coupler connected with another end of the first polarization-maintaining fiber
Implementation Method 3
a sensor consists of fiber Bragg gratings formed at a core of the third polarization-maintaining fiber
Implementation Method 4
measures strain and temperature of a detection part based on an amount of change in the wavelength of the Bragg reflected light
Implementation Method 5
a photodiode connected with the polarization-maintaining coupler via the fourth polarization-maintaining fiber, and detects Bragg reflected light from the sensor and reference light from the referential reflecting end
Implementation Method 6
a controller that detects a modulation of an interference intensity between the Bragg reflected light and the reference light, based on an intensity change of multiplexed light of the Bragg reflected light and the reference light detected by the photodiode
Data Source
AI summary
A physical quantity measuring apparatus utilizing optical frequency domain reflectometry of the invention includes a tunable laser; a first polarization-maintaining fiber; a polarization-maintaining coupler; a second polarization-maintaining fiber; a third polarization-maintaining fiber; a sensor consists of fiber Bragg gratings formed at a core of the third polarization-maintaining fiber; a fourth polarization-maintaining fiber; a photodiode detects Bragg reflected light from the sensor and reference light from the referential reflecting end; a controller detects a modulation of an interference intensity between the Bragg reflected light and the reference light, based on an intensity change of multiplexed light of the Bragg reflected light and the reference light; an incidence part inputs the measuring light; and an optical path-length adjuster arranged on the third polarization-maintaining fiber; the incidence part provided on the first polarization-maintaining fiber, or on both the second and third polarization-maintaining fibers.