Multiplexed Fiber Optic Strain Sensing via Frequency Comb
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Solution Overview
Problem
Traditional fiber optic sensors face challenges in achieving long-range, multiplexed sensing without increasing size, weight, power, and cost (SWAP-C), and existing solutions are limited by component complexity, high cost, and scalability issues, particularly in interferometric and Fabry-Perot interferometer-based systems.
Innovation Solution
A serial optical frequency comb based interrogation system is used to probe an array of fiber Fabry-Perot interferometers along a single optical fiber, allowing a single laser and detector to efficiently sense hundreds of sensors over extremely long ranges, with sensor self-noise and bandwidth scaling inversely with the number of sensors rather than the total fiber length, eliminating the need for dedicated components and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional interferometric fiber sensors with discrete components are used to achieve long-range sensing, then measurement precision is improved, but device complexity increases due to dedicated fiber couplers, wavelength division multiplexing filters, and manual construction requirements
Solution Approach 1:
The patent merges multiple discrete interferometric sensors into a single integrated fiber optic sensor using mode division multiplexing. Different spatial modes within the same fiber core carry independent sensing signals, eliminating the need for separate fiber couplers and wavelength division multiplexing filters for each sensor, thus reducing device complexity while maintaining long-range sensing capability
Solution Approach 2:
The invention creates a universal fiber optic sensor that can simultaneously perform multiple sensing functions at different locations along the fiber. A single sensor structure supports multiple spatial modes that can be independently interrogated, allowing one device to replace multiple dedicated sensors and reducing the need for manual construction of individual sensor units
2Productivity
If traditional interferometric fiber sensors use wavelength multiplexing to probe multiple sensors, then productivity is improved, but device complexity increases due to dedicated lasers and detectors for each wavelength channel
Solution Approach 1:
The patent replaces the complex wavelength multiplexing system with mode division multiplexing. Instead of using multiple lasers and detectors at different wavelengths, the system uses a single laser source and detector to interrogate multiple spatial modes within the same fiber, substituting a simpler optical system for the more complex wavelength-based approach
Solution Approach 2:
A single laser and detector combination is designed to interrogate multiple spatial modes simultaneously. The universal interrogator system can extract sensing information from different mode groups without requiring dedicated components for each channel, achieving high multiplexing capacity with reduced interrogator complexity
3Measurement precision
If fiber Fabry-Perot interferometer systems use dedicated fiber and interrogation system for each sensor, then measurement precision is improved, but weight increases due to multiple lasers, modulators, and photodetectors
Solution Approach 1:
The patent combines multiple Fabry-Perot interferometer sensing functions into a single shared fiber optic system. Multiple spatial modes within one fiber core carry independent sensing signals from different locations, eliminating the need for separate dedicated fibers and interrogation systems for each sensor, thus dramatically reducing system weight while preserving ultra-low noise measurement capability
Solution Approach 2:
The sensing function is segmented into different spatial modes within the fiber rather than requiring separate physical systems. Each mode group carries independent sensing information, allowing the system to achieve distributed sensing with a single lightweight fiber optic cable instead of multiple heavy dedicated systems
4Length of stationary object
If traditional fiber sensors increase the length of fiber to achieve long-range sensing, then length is improved, but sensor self-noise increases and bandwidth decreases
Solution Approach 1:
The patent segments the sensing function across multiple spatial modes within the fiber rather than relying on a single long fiber. Each mode group can be independently optimized for its sensing range, allowing the system to achieve extended overall coverage while maintaining low noise and high bandwidth for each individual sensing channel through mode-specific signal 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
This approach enables efficient, low-SWAP-C, long-range multiplexed fiber optic strain sensing with high sensitivity and scalability, supporting quasi-distributed sensing applications over hundreds of kilometers with minimal noise and high bandwidth, while maintaining compact sensor size and reducing transmission loss.
Implementation Method 1
probe an array of fiber Fabry-Perot interferometers fabricated along a single optical fiber
Implementation Method 2
generate a serial optical frequency comb based on the initial pulse. The serial optical frequency comb includes a train of pulses equally spaced in time and frequency
Data Source
AI summary
Multiplexed fiber optic sensors are able to monitor a multitude of sensor positions along an optical fiber from a single interrogation point. A long-standing goal is to increase the length of fiber and the number of multiplexed sensors without significantly compromising performance or increasing the size, weight, power and cost of the fiber and interrogation system. A technique is provided for performing extremely long-range, multiplexed fiber optic strain sensing in an efficient manner. This technique utilizes a serial optical frequency comb based interrogation system to probe an array of sensors placed along a single optical fiber.