Bent Multi-Core Optical Coupling Element for Direction Change
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Solution Overview
Problem
Conventional optical coupling methods between planar optical waveguides and multi-core optical fibers face issues such as increased bending loss, core-to-core crosstalk, and fiber rupture when the multi-core fiber is bent at a small diameter due to limited space, especially when the fiber direction is parallel to the waveguide plane.
Innovation Solution
The optical coupling element features a bent shape with varying core arrays and intervals between its ends, achieved by bending a holding material that integrates the cores, allowing for a fixed light input/output direction difference between ends, which reduces coupling losses and strain on the fiber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the multi-core optical fiber is bent at a small diameter to achieve direction change in limited space, then the light input/output direction can be changed, but bending loss increases
Solution Approach 1:
The patent transitions from planar bending to three-dimensional coiled configuration. The optical fibers are arranged in a coil structure with multiple layers, allowing direction change in the vertical dimension rather than forcing sharp planar bends. This dimensional transition enables gentle curvature radii that minimize bending loss while achieving the required direction change.
Solution Approach 2:
The patent employs smooth curved transitions and coiled configurations instead of sharp angular bends. The optical fibers follow continuous curved paths through the coupling element, distributing the direction change over extended arc lengths. This gradual curvature approach reduces stress concentration and minimizes bending-induced signal loss.
2Ease of operation
If the multi-core optical fiber is bent at a small diameter, then the direction can be changed, but core-to-core crosstalk increases
Solution Approach 1:
The patent applies different structural characteristics to different regions of the optical fiber bundle. In the coiled sections, fibers maintain specific spacing and orientation patterns that differ from the input/output end regions. This local structural optimization ensures that bending-induced mode coupling is minimized in specific zones while maintaining coupling efficiency at the connection points.
Solution Approach 2:
The optical fiber bundle is divided into distinct functional sections: input region, coiled transition region, and output region. Each section has optimized characteristics - the input/output regions maintain precise core alignment for coupling, while the intermediate coiled region is designed with sufficient fiber spacing and gentle curvature to prevent crosstalk during the direction transition.
3Ease of operation
If the multi-core optical fiber is bent at a small diameter, then the direction can be changed, but the probability of fiber rupture increases
Solution Approach 1:
The patent replaces sharp angular bends with gradual curved transitions throughout the optical fiber path. The coiled configuration ensures that the minimum bending radius remains above the fiber's critical threshold, distributing mechanical stress uniformly along the fiber length rather than concentrating it at sharp bend points. This significantly reduces the risk of fiber rupture while achieving the required direction change.
Solution Approach 2:
The coiled structure acts as a mechanical buffer that absorbs and distributes bending stresses before they can reach critical levels. The multi-layer coil configuration provides structural support and stress distribution, preventing localized stress concentrations that would lead to fiber failure. The design inherently cushions the fibers against excessive bending forces.
Data Source
AI summary
The present invention relates to an optical coupling element to optically couple optical elements of different kinds to each other, which is provided with a plurality of cores. In the optical coupling element a first end and a second end opposed thereto are different in at least either of a core array and a core interval. The optical coupling element has a bent shape of at least a part of the optical coupling element itself including the cores, so that a light input/output direction at the first end is different from a light input/output direction at the second end.