Multimode Waveguide Bragg Sensor for Force Sensing
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Solution Overview
Problem
Current all-optical sensors, particularly fiber Bragg grating sensors, face limitations in sensitivity, dynamic range, and cost compared to electrical and opto-electrical sensors, and existing waveguide designs are difficult to realize with low coupling losses, hindering the development of highly sensitive force sensing systems.
Innovation Solution
The use of multimode waveguides with distributed Bragg reflectors and deflecting elements that change geometry in response to forces, allowing higher order mode propagation and analysis of wavelength shifts for enhanced sensitivity, rather than relying on grating period changes, and incorporating simple waveguide designs like planar or strip geometries to minimize coupling losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fiber Bragg grating sensors are used for all-optical sensing, then remote sensing capability is enabled through low transmission loss in optical fibers, but sensitivity and dynamic range are limited compared to electrical sensors
Solution Approach 1:
The patent changes the sensing parameter from grating period modulation (conventional FBG) to effective refractive index modulation through waveguide geometry changes. This parameter change enables higher sensitivity because the effective index is more strongly affected by dimensional changes in the waveguide core, particularly when using higher order modes which have greater spatial variation and overlap with the grating structure.
Solution Approach 2:
The patent employs a composite waveguide structure combining solid cladding layers with a hollow or liquid core, creating an anti-resonant reflecting optical waveguide (ARROW). This composite structure enables unique optical confinement properties and enhances the sensitivity of the Bragg grating sensor by allowing greater interaction between the evanescent field and the grating while maintaining low transmission loss.
2Measurement precision
If sophisticated waveguide designs are used to achieve high sensitivity, then measurement precision improves, but manufacturing difficulty and coupling losses increase
Solution Approach 1:
The patent segments the waveguide structure into distinct functional regions: solid cladding layers providing mechanical support and optical confinement, and a hollow or liquid core providing the sensing region. This segmentation allows each layer to be optimized independently and simplifies the fabrication process compared to monolithic complex waveguide designs.
Solution Approach 2:
The patent uses thin film deposition techniques to create the layered waveguide structure with precise thickness control. The hollow core waveguide can be formed using released sacrificial layers or direct deposition methods, enabling simple planar or strip geometries that are easier to manufacture than previously required sophisticated designs while maintaining high sensitivity through higher order mode propagation.
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 significantly improves the sensitivity of all-optical sensors by leveraging higher order mode propagation and wavelength shifts, enabling more robust and cost-effective force sensing systems with reduced coupling losses, thus overcoming the limitations of traditional FBG sensors.
Implementation Method 1
at least one distributed Bragg reflector
Implementation Method 2
a waveguide accommodating a non-solid core for confining light
Data Source
Figure 1a~1d
Figure 2~3b
Figure 4~5
AI summary
The present invention relates to an all-optical sensor utilizing effective index modulation of a waveguide and detection of a wavelength shift of reflected light and a force sensing system accommodating said optical sensor. One embodiment of the invention relates to a sensor system comprising at least one multimode light source, one or more optical sensors comprising a multimode sensor optical waveguide accommodating a distributed Bragg reflector, at least one transmitting optical waveguide for guiding light from said at least one light source to said one or more multimode sensor optical waveguides, a detector for measuring light reflected from said Bragg reflector in said one or more multimode sensor optical waveguides, and a data processor adapted for analyzing variations in the Bragg wavelength of at least one higher order mode of the reflected light.