Coherent Optical Fiber Sensing with Spatial Mode Multiplexing
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Solution Overview
Problem
Current optical fiber sensor systems cannot simultaneously utilize both forward and backward propagating signals efficiently for high spectral efficiency and low coupling loss, and they struggle with achieving high spatial resolution and accurate measurements of multiple measurands in harsh environments, requiring additional communication cables and multiple electronic sensors.
Innovation Solution
A distributed multi-channel coherent optical fiber sensing system using Few-Mode Fibers or Multi-Mode Fibers, spatial mode converters, polarization and mode multiplexing, and spatial filters to transmit and sense signals simultaneously in both directions, enabling cost-effective and high-resolution measurements of various parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical couplers (optical isolators and optic terminators) are applied to prevent unwanted feedback and absorb light, then the reliability of signal transmission is improved, but the optical power loss increases and information is wasted
Solution Approach 1:
The patent merges the functions of optical isolators and terminators by using a single circulator component to handle both forward signal transmission and backward reflected signal routing. This consolidation eliminates multiple coupling interfaces, reducing optical power loss while maintaining reliable signal transmission through efficient bidirectional signal management.
Solution Approach 2:
The circulator serves multiple functions simultaneously: it acts as an optical isolator for forward signals, routes backward reflected signals to the receiver, and enables dual-functionality for both communication and sensing. This multi-functionality reduces the need for separate components, minimizing coupling losses while ensuring reliable operation.
2Reliability
If separate communication cables are deployed for signal transmission in harsh environments, then the reliability of communication is improved, but the device complexity and maintenance costs increase
Solution Approach 1:
The patent combines communication and sensing functions into a single optical fiber system. The same fiber that carries communication signals also performs distributed sensing through Brillouin scattering measurement, eliminating the need for separate sensing cables and reducing overall system complexity while maintaining reliable operation in harsh environments.
Solution Approach 2:
The optical fiber system is designed to perform dual functions: transmitting communication signals and simultaneously providing distributed temperature and strain sensing. This multi-functionality is achieved through coherent detection and Brillouin scattering measurement, allowing a single fiber to replace what would traditionally require separate communication and sensing infrastructure.
3Measurement precision
If multiple electronic point sensors are used to measure different measurands, then the measurement precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent combines multiple sensing capabilities (temperature and strain measurement) into a single distributed fiber optic sensor system. By using Brillouin scattering characteristics and coherent detection, the system can simultaneously measure multiple measurands along the entire fiber length, replacing numerous electronic point sensors with a single distributed sensing platform.
Solution Approach 2:
The fiber optic sensor system provides universal sensing capability for multiple physical parameters including temperature, strain, and potentially other measurands. The system uses a single fiber infrastructure with coherent detection and Brillouin scattering analysis to deliver precise measurements across multiple parameters simultaneously, eliminating the need for separate sensor systems for each measurand.
4Measurement precision
If Single-Mode Fibers with Brillouin scattering measurement are used for temperature and strain sensing, then the measurement capability is improved, but the spatial resolution deteriorates
Solution Approach 1:
The patent changes the detection parameter from traditional Brillouin frequency shift measurement to coherent detection of backscattered light. By using coherent detection with phase-sensitive measurement, the system achieves enhanced spatial resolution while maintaining temperature and strain measurement capabilities. The parameter change in detection methodology enables simultaneous improvement in both measurement capability and spatial resolution.
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 system allows for simultaneous signal transmission and distributed sensing with high sensitivity and low coupling loss, reducing maintenance costs and enabling accurate measurements of multiple parameters like temperature, strain, pressure, and acceleration with improved spatial resolution.
Implementation Method 1
converting, using a spatial mode converter, an input signal into a plurality of spatial modes
Implementation Method 2
performing polarization multiplexing and mode multiplexing, using a polarization multiplexer and a mode multiplexer, respectively, on the input signal
Implementation Method 3
performing polarization multiplexing and mode multiplexing, using a polarization multiplexer and a mode multiplexer, respectively, on the input signal
Implementation Method 4
applying, using at least one spatial filter in each of a forward and a backward direction within the fiber optic medium, the plurality of spatial modes within the fiber optic medium to transmit the input signal and perform distributed fault sensing on the input signal simultaneously
Implementation Method 5
Optical fiber technology is ideal for telecommunication systems for its low-loss, high-bandwidth, low-dispersion advantages
Data Source
AI summary
A method and system are provided. The method includes converting, using a spatial mode converter, an input signal into a plurality of spatial modes and performing polarization multiplexing and mode multiplexing, using a polarization multiplexer and a mode multiplexer, respectively, on the input signal. The method further includes injecting the input signal into a fiber optic medium. The method additionally includes applying, using at least one spatial filter in each of a forward and a backward direction within the fiber optic medium, the plurality of spatial modes within the fiber optic medium to transmit the input signal and perform distributed fault sensing on the input signal simultaneously.