Circular Grating Coupler for Ring-Core Fiber Mode Multiplexing
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Solution Overview
Problem
Current optical devices, particularly those using multi-mode fibers, face limitations in efficiently propagating and multiplexing information across multiple spatial modes, which restricts their ability to carry and process data effectively compared to single-mode fibers.
Innovation Solution
The development of a circular grating coupler with concentric ridges and grooves, combined with radial waveguides, enables efficient coupling and multiplexing of polarization and propagation modes in ring-core optical fibers, allowing for increased data throughput by forming focused azimuthally or radially polarized beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-mode fibers are used to propagate multiple spatial modes, then data transmission capacity is increased, but coupling efficiency and mode multiplexing performance deteriorate
Solution Approach 1:
The patent employs a circular grating coupler with concentric ring structures instead of conventional linear gratings. The circular symmetry and curved geometry of the grating periods are specifically designed to match the azimuthal mode distribution of ring-core optical fibers, enabling efficient coupling of multiple spatial modes while maintaining high coupling efficiency through geometric resonance conditions
Solution Approach 2:
The grating coupler features spatially varying local properties including position-dependent grating period, depth, and azimuthal orientation. These locally optimized parameters are tailored to excite specific propagation modes at different angular positions around the ring-core fiber, enabling independent control and multiplexing of multiple modes with high efficiency
2Ease of manufacture
If conventional linear grating couplers are used, then manufacturing is simplified, but coupling efficiency to ring-core fibers deteriorates
Solution Approach 1:
The invention transitions from linear to circular grating geometry, where the grating lines are arranged in concentric rings around the ring-core fiber. This curved configuration naturally aligns with the azimuthal symmetry of the fiber modes, dramatically improving coupling efficiency while remaining compatible with standard lithographic fabrication processes through radial coordinate system patterning
3Quantity of substance
If multiple spatial modes are multiplexed, then information carrying capacity is increased, but mode discrimination and demultiplexing performance deteriorates
Solution Approach 1:
The circular grating coupler is designed with azimuthally segmented regions where different grating parameters (period, depth, orientation) are assigned to different angular sectors. Each segment is optimized to couple to or filter specific propagation modes, enabling precise mode discrimination and demultiplexing by spatially separating mode components around the circular structure
Solution Approach 2:
The grating employs periodic variations in grating parameters around the circular structure, with the period and phase of these variations tailored to resonate with specific propagation modes. This periodic modulation creates distinct spectral signatures for different modes, enabling precise discrimination through wavelength or angular selective coupling
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 solution enhances data transmission capacity and resolution by efficiently exciting and demultiplexing propagation modes within ring-core optical fibers, offering improved performance over traditional single-mode fiber links.
Implementation Method 1
circular grating coupler with concentric ridges and grooves
Implementation Method 2
optical resonator comprising nested closed optical regions in form of concentric rings
Implementation Method 3
radial waveguides formed over the planar substrate, with first ends that terminate near an outermost one of the ridges
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2E
AI summary
An optical device includes an optical grating coupler and a plurality of optical waveguides coupled thereto. The optical grating coupler is formed along a planar surface of a substrate, and includes a pattern formed by ridges concentrically located on the surface about a center thereon. Each adjacent pair of ridges is separated by a groove. Each waveguide of the plurality of waveguides is oriented about radially with respect to the center, and has a first end that terminates near an outermost one of the ridges. The first ends are about uniformly spaced along the outermost one of the ridges.