Dual-Frequency Optical Pump Rayleigh Backscattering Measurement
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Solution Overview
Problem
Current optical time domain reflectometry (OTDR) technologies face limitations such as polarization fading, nonlinear response, and inability to measure absolute values of temperature or strain directly, which restricts their sensing range, resolution, and measurement speed.
Innovation Solution
The process involves injecting two optical pumps with different frequencies into an optical fiber, where the first and second optical frequencies have the same frequency difference with respect to a constant source frequency, allowing for simultaneous detection and analysis of Rayleigh backscattered signals to determine physical quantities like strain, temperature, and pressure, while ensuring orthogonal polarizations to avoid polarization fading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single frequency optical pump is used for OTDR measurement, then device complexity is reduced, but measurement precision deteriorates due to polarization fading and nonlinear response
Solution Approach 1:
The single optical pump is segmented into two optical pumps with different frequencies. This segmentation allows the system to measure different polarization components separately, eliminating polarization fading effects and enabling linear response for accurate physical quantity measurement while maintaining relatively simple device configuration.
2Length of stationary object
If broadband light is used for Rayleigh backscattering measurement, then sensing range is extended, but measurement precision deteriorates due to reduced signal intensity
Solution Approach 1:
The system uses periodic pulse injection of two different frequency optical pumps into the optical fiber. This periodic action allows for time-domain analysis of the backscattered signals, enabling both extended sensing range through pulse propagation and maintained measurement precision through coherent detection and signal processing of the periodic returns.
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 enhances the signal-to-noise ratio, extends the sensing range, reduces measurement time, and improves spatial resolution, enabling more accurate and efficient measurement of physical quantities along the optical fiber.
Implementation Method 1
Rayleigh scattering is the interaction of a light pulse with material impurities (a typical example would be the scattering of sunlight by dust particles in the atmosphere giving to the sky different colors depending on the incident angle of the sun light)
Implementation Method 2
ensuring orthogonal polarizations to avoid polarization fading
Data Source
Figure 1~2
Figure 3~4
Figure 5a~6c
AI summary
The invention concerns a process comprising the following steps: - Simultaneously injecting in an optical fiber (3) a first optical pump (31) at a first optical frequency that evolves in time or not, and a second optical pump (32) at a second optical frequency that evolves in time or not, the first optical frequency and the second optical frequency being different at each given time, - a first detection of a first Rayleigh backscattered signal (41) at the first optical frequency from the optical fiber, - a second detection, separated from the first detection, of a second Rayleigh backscattered signal (42) at the second optical frequency from the optical fiber, - analyzing the detected first Rayleigh backscattered signal and the detected second Rayleigh backscattered signal.