Mode Field Adapter for Hollow Core Fiber Coupling
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Solution Overview
Problem
The existing methods for coupling optical fibers with different mode field diameters, such as hollow core and solid core fibers, are costly and complex due to the need for fiber-based mode field converters, limiting the effective use of hollow core fibers in applications like 5G fronthaul networks.
Innovation Solution
A mode field adapter using collimating lenses with specific focal lengths and filters to adapt the mode field diameter between hollow core and solid core optical fibers, allowing for efficient coupling and reducing network complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fiber-based mode field converters are used to couple hollow core and solid core optical fibers, then mode field adaptation is achieved, but device complexity and manufacturing cost increase substantially
Solution Approach 1:
The patent introduces an optical beam expander as an intermediary device that converts the optical beam from the hollow core fiber into an expanded beam, which is then coupled to the solid core fiber. This intermediary approach avoids the need for complex fiber-based mode field converters while achieving effective mode field adaptation between the two different fiber types.
Solution Approach 2:
The patent replaces the mechanical fiber splicing and fiber-based conversion system with an optical beam manipulation system using lenses and beam expanders. This substitution eliminates the need for precise mechanical alignment and fiber handling, thereby reducing device complexity and manufacturing cost while maintaining mode field adaptation functionality.
2Adaptability or versatility
If fiber-based mode field converters are used to couple hollow core and solid core optical fibers, then mode field adaptation is achieved, but manufacturing cost increases substantially
Solution Approach 1:
The optical beam expander serves as a simpler, more manufacturable intermediary device compared to fiber-based mode field converters. The beam expander uses standard optical components (lenses, mirrors) that are easier and less costly to manufacture and assemble than specialized fiber converters, thereby reducing manufacturing cost while achieving the required mode field adaptation.
Solution Approach 2:
The patent employs standard optical components such as lenses and beam expanders that are commercially available, easier to manufacture, and less expensive than custom fiber-based converters. These components can be readily replaced or adjusted, reducing the overall manufacturing cost of the coupling system.
3Length of stationary object
If hollow core optical fibers are used in 5G fronthaul networks, then transmission distance and coverage area increase, but mode field diameter mismatch with solid core fibers creates coupling difficulty
Solution Approach 1:
The optical beam expander acts as a mediator that bridges the mode field diameter mismatch between hollow core and solid core fibers. By expanding the optical beam from the hollow core fiber to match the larger mode field diameter of the solid core fiber, the beam expander enables efficient coupling and maintains adaptability while allowing the use of hollow core fibers for extended transmission distances.
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 adapter enables efficient optical coupling between hollow core and solid core fibers, increasing the distance and coverage area of 5G fronthaul networks while reducing the need for costly fiber splicing and network complexity.
Implementation Method 1
The first collimating lens is configured to receive a diverging optical beam from the first optical fiber, and generate an expanded optical beam therefrom
Implementation Method 2
The second collimating lens is configured to receive at least a portion of the expanded optical beam, generate a first converging optical beam therefrom
Data Source
AI summary
Mode field adapters and methods of making mode field adapters that include a plurality of ports each having a collimating lens. At least one port is configured to receive a hollow core optical fiber and has a collimating lens with characteristics optimized for hollow core optical fibers. One or more other ports are configured to receive solid core optical fibers and have collimating lenses with characteristics optimized for solid-core fibers. The focal lengths of the lenses are selected so that the ratio of focal lengths between collimating lenses for hollow core and solid core optical fibers is the substantially the same as the ratio between the mode field diameters of the hollow core and solid core optical fibers. Mode field adapters may include one or more bandpass filters configured to selectively couple portions of an optical beam between a common port and different channel ports of the mode field adapter.