Multi-Mode Optical Fiber Measurement System for Simultaneous Parameter Sensing
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Solution Overview
Problem
Current optical fiber measurement systems face limitations in simultaneously measuring multiple parameters such as temperature, strain, pressure, and radiation due to the complexity of modal properties and limited resolution, especially under non-stationary conditions, where multiple factors influence the effective refractive index.
Innovation Solution
An optical fiber measurement system with a monotonically tuneable wavelength source, a multi-port interferometer, and a processing unit that excites multiple modes with different effective refractive indices, allowing for simultaneous measurement of various environmental parameters by analyzing interference signals and correcting for non-linearity, using a multi-core optical fiber with anti-reflection coatings to minimize noise and enhance signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple modes with different effective refractive indices are excited in the optical fibre, then the number of simultaneously measurable parameters increases, but the device complexity increases due to modal property management
Solution Approach 1:
The patent segments the optical fiber into multiple measurement sections, each capable of measuring different parameters. By using mode division multiplexing, different spatial modes are assigned to measure different physical quantities (temperature, strain, pressure, radiation) at the same location, effectively segmenting the measurement function across multiple modes while using a single fiber.
Solution Approach 2:
The optical fiber sensor system is designed to perform multiple measurement functions simultaneously using different propagating modes. The same physical fiber structure serves as a universal platform for measuring temperature, strain, pressure, and radiation by exploiting the different sensitivities of various modes to these parameters, eliminating the need for separate sensor systems.
2Measurement precision
If conventional single-mode optical fibre measurement is used, then the device complexity is low, but the measurement precision and resolution are limited under non-stationary conditions
Solution Approach 1:
The patent changes the operational parameters of the optical fiber by utilizing multiple propagation modes with different effective refractive indices. By monitoring changes in mode effective indices and their evolution over time, the system achieves higher measurement precision for multiple parameters simultaneously, overcoming the limitations of single-mode measurements under non-stationary conditions.
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, high-resolution measurement of multiple parameters along the entire length of the optical fiber, reducing measurement errors and increasing the number of parameters that can be simultaneously measured, while maintaining stability and accuracy under varying environmental conditions.
Implementation Method 1
An optical fibre based measurement system with a monotonically tuneable wavelength source, a multi-port interferometer, and a processing unit that excites multiple modes with different effective refractive indices, allowing for simultaneous measurement of various environmental parameters by analyzing interference signals
Implementation Method 2
Rayleigh scattering is the scattering of light under the influence of inhomogeneity of the medium in which light propagates. One disadvantage of techniques involving the utilization of this phenomenon is the lack of direct information about temperature changes in the studied environment.
Implementation Method 3
Raman effect is utilized to measure temperature using the Stokes and anti-Stokes signal intensity difference analysis in the optical fibre length function. The light power analysis enables the determination of the absolute temperature, unfortunately with relatively small resolution—at the level of 1 m—in the optical fibre length function.
Implementation Method 4
Exploitation of Brillouin effect to measure temperature involves analysing the frequency of propagation of the acoustic wave generated in the optical fibre excited by light with high intensity.
Implementation Method 5
using a multi-core optical fiber with anti-reflection coatings to minimize noise and enhance signal-to-noise ratio
Data Source
AI summary
Optical fibre based measurement system having a system for generating radiation (Z) with monotonically tuneable wavelength during sweep periods, an optical path (T) and a detector (D) connected to the system for generating radiation (Z) via the optical path (T). The optical path (T) comprises the interferometer (I) comprising the multi-port element (EW) and the attached measuring optical fibre (F) sensitive to at least two environmental parameters, the mode excitation system (P) adapted for excitation in the measuring optical fibre (F) of at least the measuring mode (Mn1) with the first effective refractive index and the measuring mode (Mn2) with the second effective refractive index, having different sensitivity to these two parameters. The measurement system comprises the processing unit (UP) to which the detector (D) is connected via the analogue-to-digital converter (ADC), and the processing unit (UP) is adapted to generate the control signal for the system for generating radiation (Z). The object of the invention is also the method of measuring at least two parameters, and the computer program product.