Optical Fiber Sensor Distance Resolution via Frequency Sweeping
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Solution Overview
Problem
Conventional acoustic wave optical fiber sensors used in petroleum and natural gas prospecting have limited distance resolution, which affects the accuracy of seismic prospecting and strain detection methods.
Innovation Solution
An optical fiber sensor system that transmits two lights with different wavelengths, where at least one wavelength varies over time, and a measuring unit detects the temporal variation of the optical phase by measuring the interference state of the back-scattered lights, allowing for improved distance resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If OTDR method is used for acoustic wave optical fiber sensing, then the system is simple and widely used, but the distance resolution is limited to at least about 1 m
Solution Approach 1:
The patent changes the fundamental measurement parameter from time-domain reflectometry to frequency-domain interferometry. By sweeping the optical frequency and measuring interference patterns, the system achieves distance resolution of about 10 cm or better, overcoming the 1 m limitation of OTDR while maintaining practical system complexity
Solution Approach 2:
The patent replaces the mechanical/time-based measurement approach of OTDR with an optical interference-based frequency domain approach. This substitution enables higher resolution measurements by utilizing the wave nature of light and interference phenomena rather than relying on time-of-flight measurements
2Measurement precision
If OFDR method is used to improve distance resolution, then the distance resolution can be improved by narrowing frequency band width, but the measurement time and complexity increase
Solution Approach 1:
The patent employs periodic frequency sweeping with a triangular or linear chirp pattern. By repeatedly sweeping through the frequency range and accumulating interference measurements, the system achieves high distance resolution without requiring excessively long measurement times, as the periodic nature allows for efficient data collection and processing
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 enhanced distance resolution, enabling more accurate detection of acoustic waves and improved positioning of reservoir layers and fissures, thereby enhancing the precision of seismic prospecting and strain detection.
Implementation Method 1
a transmitting unit configured to output two lights into an optical fiber, wavelengths of the two lights being different from each other at a specific time, and at least one of the wavelengths of the two lights varying with time
Implementation Method 2
a measuring unit configured to receive back-scattered light output from the optical fiber and detect a temporal variation of an optical phase at an arbitrary interval in a longitudinal direction of the optical fiber by measuring measure an interference state of the two lights
Implementation Method 3
receive back-scattered light output from the optical fiber
Data Source
AI summary
An optical fiber sensor includes: a transmitting unit configured to output two lights into an optical fiber, wavelengths of the two lights being different from each other at a specific time, and at least one of the wavelengths of the two lights varying with time; and a measuring unit configured to receive back-scattered light output from the optical fiber and detect a temporal variation of an optical phase at an arbitrary interval in a longitudinal direction of the optical fiber by measuring measure an interference state of the two lights.