Non-linear Optical Fiber Strain Gauge System
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Solution Overview
Problem
Conventional optical fiber-based strain measurement systems have a suboptimal signal-to-noise ratio and lack real-time measurement capabilities due to the small magnitude of the return signal and the need to sweep the source signal across a range of wavelengths for each measurement.
Innovation Solution
A non-linear optical fiber strain measurement system using two light sources with different frequencies, coupled via a 3:1 coupler, and detectors that generate a return signal at a third predictable wavelength, allowing for real-time strain measurement with improved signal-to-noise ratio through second-order polarization effects and Bragg gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional linear source signals are used in optical fiber strain measurement systems, then the system structure is simple, but the signal-to-noise ratio of the return signal is low
Solution Approach 1:
The patent changes the fundamental parameter of the source signal from linear to non-linear (hyperbolic secant squared function), which transforms the return signal characteristics and dramatically improves the signal-to-noise ratio while maintaining system simplicity
Solution Approach 2:
The patent utilizes the natural vibration resonances of the optical fiber at specific frequencies, injecting non-linear source signals at these resonant frequencies to amplify the return signal and improve measurement precision
2Productivity
If wavelength sweeping is used to detect peak level for strain measurement, then the measurement method is straightforward, but real-time measurement capability is lost due to delay
Solution Approach 1:
The patent performs preliminary tuning of the non-linear source signal frequency to match the optical fiber's vibration resonance frequency before measurement, which pre-optimizes the system for real-time detection and eliminates the need for continuous wavelength sweeping
Solution Approach 2:
The patent employs periodic modulation of the non-linear source signal at the optical fiber's resonant frequency, enabling continuous real-time measurement through periodic detection rather than sequential wavelength sweeping
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 achieves a significantly higher signal-to-noise ratio and enables real-time strain measurement by utilizing non-linear source signals and detectors, simplifying the detection process and enhancing measurement responsiveness.
Implementation Method 1
an optical fiber having a first end, a second end, and a central portion secured between two predetermined fixed points
Implementation Method 2
utilizing non-linear source signals and detectors, simplifying the detection process and enhancing measurement responsiveness
Implementation Method 3
A non-linear optical fiber strain measurement system using two light sources with different frequencies
Implementation Method 4
Bragg gratings can be written into the optical fiber in such systems to produce a larger return signal
Data Source
AI summary
A system for measuring strain includes an optical fiber having a central portion secured between two fixed points. A first light source outputs light at a first frequency and a second light source outputs light at a second different frequency. The two light sources are both coupled to a first end of the optical fiber. A back scatter detector is also coupled to the first end to receive a return light signal from the optical fiber and outputs a signal based thereon. A forward scatter detector is coupled to a second end of the optical fiber to receive a forward light signal from the optical fiber and outputs a signal based thereon. A processor receives the signals from the back scatter detector and the forward scatter detector and generates an output signal proportional to the strain between the two fixed points based on the received signals.