Optical Sensor Slow Light Sensitivity
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Solution Overview
Problem
Existing optical sensors do not consistently achieve sensitivity enhancement using slow light, and there is a lack of general recipes for determining when slow-light enhancement is effective, particularly in fiber sensors for velocity, rotation, strain, and temperature measurements.
Innovation Solution
Specific fiber sensor configurations, such as interferometric fluid and tangential velocity sensors, utilize slow light generated by techniques like Bragg fibers or photonic-bandgap fibers, with group indices significantly greater than one, to enhance sensitivity by manipulating the group velocity and phase velocity ratio, thereby increasing the sensitivity to fluid flow, rotation, strain, and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If slow light is used in optical sensors, then sensitivity enhancement is achieved, but the device complexity increases due to the need for specialized fiber configurations
Solution Approach 1:
The patent changes the group velocity parameter of light by using specialized fiber configurations (Bragg fibers, photonic-bandgap fibers) to achieve slow light conditions. This parameter change enables sensitivity enhancement in optical sensors by increasing the interaction time between light and the sensing medium, thereby improving measurement precision without requiring complete system redesign
Solution Approach 2:
The patent employs composite fiber structures such as Bragg fibers and photonic-bandgap fibers that combine multiple materials with different refractive indices. These composite structures create the necessary optical conditions for slow light propagation while maintaining the fiber's mechanical and optical properties, thus achieving sensitivity enhancement without excessive device complexity
2Measurement precision
If group velocity is reduced to enhance sensitivity, then measurement precision improves, but the speed of signal transmission decreases
Solution Approach 1:
The patent utilizes periodic modulation of the fiber structure (such as periodic variations in refractive index in Bragg fibers) to create slow light conditions. This periodic action allows the light to experience multiple reflections and phase shifts that effectively reduce group velocity for sensing purposes, while the overall system can maintain acceptable signal transmission speeds through optimized design parameters
Solution Approach 2:
The patent applies local quality changes by creating specific regions within the fiber structure that have different optical properties. For example, in photonic-bandgap fibers, certain radial regions have different refractive indices that locally slow down light propagation. This localized approach allows sensitivity enhancement in the sensing region while minimizing the impact on overall signal transmission speed
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
The use of slow light in these configurations enhances the sensitivity of optical sensors by increasing the time delay between counterpropagating signals, allowing for more precise measurements of velocity, rotation, strain, and temperature, depending on the group index and phase index ratios.
Implementation Method 1
The optical waveguide is configured to receive a first optical signal from the at least one optical coupler. The first optical signal has a group velocity and a phase velocity while propagating through the optical waveguide, with the group velocity less than the phase velocity.
Implementation Method 2
An interference between the first optical signal and a second optical signal is affected by perturbations to the optical sensor.
Data Source
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AI summary
An optical sensor comprising: at least one optical coupler (94) an optical waveguide (92) comprising a plurality of loops, the optical waveguide in optical communication with the at least one optical coupler and mechanically decoupled from the at least one optical coupler such that the at least one optical coupler and the optical waveguide can be moved relative to one another with a rotation of the optical waveguide about an axis of symmetry of the plurality of loops, the optical waveguide configured to receive a first optical signal from the at least one optical coupler, wherein the first optical signal has a group velocity, and a phase velocity while propagating through at least a portion of the optical waveguide, the group velocity less than the phase velocity, wherein an interference between the first optical signal and a second optical signal is affected by the rotation of the optical waveguide about the axis of symmetry; and an optical detector (D) configured to detect interference between the first optical signal and the second optical signal.