Fiber Optic Gyroscope Hybrid Coupler Sensitivity
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Solution Overview
Problem
Interferometric fiber optic gyroscopes (FOGs) face limitations in sensitivity due to their design, particularly with 2×2 and 3×3 couplers, which affect their ability to accurately measure angular velocity, as they are either less sensitive or operate in less sensitive parts of their response characteristic.
Innovation Solution
The design incorporates a fiber coil-based gyroscope using integrated on-chip waveguide couplers in various configurations, including 2×2 and 3×3 waveguide couplers, photodetectors, and a light source on a substrate like Si or SOI, with multiple quantum well (MQW) waveguides for phase correction, and electronic circuits for signal processing, enhancing sensitivity by utilizing a combination of 2×2 and 3×3 couplers and MQW waveguides for improved phase modulation and birefringence control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 2×2 fiber couplers are used in FOG design, then the device can be manufactured with standard components, but the sensitivity is reduced and requires additional phase modulators
Solution Approach 1:
The patent combines 2×2 and 3×3 couplers in a hybrid configuration where the 3×3 coupler provides high-sensitivity detection at the optimal operating point while the 2×2 coupler enables standard manufacturing. This merging allows the system to achieve both manufacturability and high sensitivity without requiring additional phase modulators.
Solution Approach 2:
The patent changes the operating parameters by using 3×3 couplers that inherently operate at the most sensitive part of the response characteristic. This parameter change eliminates the need for ninety-degree phase modulators required by 2×2 coupler systems, thereby improving sensitivity while maintaining manufacturability.
2Measurement precision
If 3×3 fiber couplers are used in FOG design, then the device operates at the most sensitive part of the response characteristic, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the coupler system into a hybrid configuration combining 2×2 and 3×3 couplers. The 3×3 coupler is used specifically for the sensitive detection function, while the 2×2 coupler handles other signal paths. This segmentation allows the system to achieve high sensitivity where needed while maintaining simpler components elsewhere, reducing overall manufacturing complexity.
3Measurement precision
If ninety degrees phase modulators are incorporated in 2×2 coupler based gyroscopes, then the sensitivity can be improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the ninety-degree phase modulator from the system by transitioning to a 3×3 coupler-based design. The 3×3 coupler inherently operates at the most sensitive part of the response characteristic, eliminating the need for the phase modulator and its associated complexity and cost.
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 configuration achieves higher sensitivity and accuracy in measuring angular velocity, enabling the determination of three-axis components of platform movement with improved sensitivity and cost-effectiveness, addressing the limitations of existing FOG designs.
Implementation Method 1
the three waveguides are in proximity over a certain length to produce light coupling between them
Implementation Method 2
a first absorber device which absorb any optical energy not coupled to the outer waveguide
Implementation Method 3
the input ends of the outer waveguides of said 3×3 waveguide coupler are interfaced with first and second photodetectors
Implementation Method 4
Interferometric fiber optic gyroscopes (FOG) rely on Sagnac effect to measure the angular velocity of a moving object. The clockwise (CW) wave and counter clockwise (CCW) wave in a fiber coil will undergo Doppler shift when the coil rotates
Implementation Method 5
MQW waveguides can be tuned to achieve any phase correction due to birefringence introduced by coil or other components
Data Source
AI summary
This invention describes a gyroscope using a fiber coil which is coupled using integrated on-chip 3×3 and 2×2 couplers in coplanar as well as non-coplanar (NCP) configuration along with photodetectors, light sources, and processing electronics using Si, SOI, and InGaAs-on-Si, and other substrates. In one embodiment, a high sensitivity gyroscope using a combination of 2×2 and 3×3 waveguide couplers is described. The signals from three photodetectors can be used to generate feedback signals to produce high sensitivity. Still in another embodiment, usage of multiple quantum well (MQW) waveguides is illustrated. MQW waveguides can be tuned to achieve phase modulation/correction in couplers.