Coherent Receiver Sensor for Absolute Strain and Temperature
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Solution Overview
Problem
Existing optical fiber sensors face challenges in accurately determining temperature and strain due to the non-absolute nature of Rayleigh measurements, requiring controlled environments and reference data, which can be lost or incompatible with new equipment.
Innovation Solution
A temperature or strain distribution sensor utilizing a pair of tunable laser sources and a semiconductor optical amplifier to determine both Brillouin and Rayleigh traces, allowing for absolute referencing of Rayleigh measurements without the need for controlled environments or specific instrumentation, using a pair of laser beams with a predetermined offset frequency shift to acquire Brillouin and Rayleigh spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Rayleigh measurements are used for temperature and strain determination, then measurement capability is provided, but the measurements are non-absolute and require controlled environments and reference data
Solution Approach 1:
The patent combines Brillouin scattering measurements and Rayleigh scattering measurements into a single sensor system. The Brillouin measurements provide absolute temperature and strain references, while the Rayleigh measurements provide high-resolution spatial information. By merging these two measurement techniques, the system achieves both absolute accuracy and high measurement capability without requiring separate controlled environments or reference data storage.
Solution Approach 2:
The patent uses Brillouin scattering as an intermediary to provide absolute reference measurements that calibrate the non-absolute Rayleigh measurements. The Brillouin frequency shift serves as a mediator that translates environmental conditions (temperature and strain) into absolute reference values, which then enable the Rayleigh measurements to be interpreted accurately without requiring controlled environments or stored reference data.
2Measurement precision
If reference data is stored for Rayleigh measurements, then accurate temperature and strain determination is possible, but the reference data can be lost or become incompatible with new equipment
Solution Approach 1:
The patent enables the sensor system to generate its own absolute reference measurements on-demand using Brillouin scattering, eliminating the need to store reference data. The system performs self-calibration by measuring the Brillouin frequency shift at each measurement point, which provides an absolute reference that is inherently tied to the current environmental conditions. This self-service approach ensures that the system is always self-sufficient and immune to reference data loss or compatibility issues.
Solution Approach 2:
The patent performs preliminary Brillouin measurements to establish absolute reference values before conducting Rayleigh measurements. By pre-establishing the Brillouin frequency shift as an absolute reference, the system prepares the necessary calibration information in real-time, eliminating the need to rely on previously stored reference data and ensuring compatibility with any equipment that implements the same measurement principles.
3Measurement precision
If Brillouin and Rayleigh traces are determined using a coherent receiver, then absolute referencing is achieved, but the system complexity increases
Solution Approach 1:
The patent designs the coherent receiver to perform multiple functions: it detects both Brillouin scattered light and Rayleigh scattered light using the same hardware platform. The coherent detection scheme serves as a universal measurement mechanism that can extract both the frequency shift information (for Brillouin absolute referencing) and the backscatter intensity information (for Rayleigh high-resolution sensing) from the same optical signal, thereby reducing overall system complexity despite the advanced detection capability.
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 determination of temperature and strain in optical fibers without the need for reference data or controlled environments, providing absolute referencing and high spatial resolution, and eliminating the requirement for maintaining reference data.
Implementation Method 1
Brillouin scattering occurs when light passing through a transparent medium interacts with periodic spatial and temporal variations of the refractive index created by acoustic waves. Brillouin scattering, which is dependent on environmental variables such as strain and temperature, may be used to sense mechanical strain and/or temperature in optical fibers.
Implementation Method 2
Compared to Brillouin scattering, Rayleigh scattering pertains to the elastic scattering of light or other electromagnetic radiation by particles. Rayleigh scattering may be used to identify anomalies in transmission of a signal along an optical fiber.
Implementation Method 3
With respect to absorption, light may be absorbed in optical fiber material as the energy of the light is converted to heat.
Data Source
AI summary
According to examples, a temperature or strain distribution sensor may include a photodiode to acquire a beat frequency between a first laser beam and a second laser beam. A modulator may modulate the first laser beam that is to be injected into a device under test (DUT). A coherent receiver may acquire a backscattered signal from the DUT, and use the second laser beam as a local oscillator to determine a Brillouin trace with respect to the DUT. The Brillouin trace may be used to determine a Brillouin frequency shift and a Brillouin power for the DUT to implement an absolute referencing of a Rayleigh reference trace. The coherent receiver may determine, relative to the Rayleigh reference trace, a further Brillouin frequency shift and a Rayleigh frequency shift to determine a temperature or a strain associated with the DUT.