Multicore Fiber Cladding Shape for Easier Rotational Alignment
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Solution Overview
Problem
Multicore fibers with non-circular outer shapes face alignment issues due to the multicore fiber, especially when the multicore fiber is used for long-distance optical signal transmission, where alignment accuracy is crucial but difficult due to spherical aberration and rotational position challenges, particularly with D-type cladding shapes.
Innovation Solution
A multicore fiber design with a cladding having a non-rotationally symmetric outer surface, featuring a first outer circumferential surface with a larger curvature radius than a second surface, allowing for easier alignment and reduced spherical aberration during side-view alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a D-type cladding outer shape is used, then alignment accuracy is improved, but spherical aberration increases making alignment difficult
Solution Approach 1:
The cladding outer shape is designed as asymmetric D-type with a planar portion and a curved portion, creating a unique orientation that enables accurate alignment through side-view observation while maintaining favorable optical coupling characteristics
Solution Approach 2:
Different portions of the cladding outer surface have different curvatures - the planar portion provides a reference for alignment while the curved portion optimizes optical coupling, with at least one core positioned to face the curved portion for enhanced performance
2Ease of operation
If light is incident from the planar portion of the cladding, then alignment can be performed, but spherical aberration becomes large
Solution Approach 1:
The cladding outer surface is divided into regions with different optical properties - the planar portion serves as an alignment reference while the curved portion with larger radius of curvature reduces spherical aberration for light incident from that direction
Solution Approach 2:
The problem is solved by transitioning from a conventional circular cross-section to a D-type cross-section with distinct planar and curved portions, creating additional geometric dimensions that simultaneously enable alignment and reduce aberration
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 design facilitates easier alignment and reduces spherical aberration, enhancing the accuracy of rotational positioning and attenuating unwanted higher-order modes, thereby improving alignment efficiency and signal transmission quality.
Implementation Method 1
at least a part of the first outer circumferential surface bulges outside the cladding with a curvature radius larger than that of the second outer circumferential surface... the spherical aberration may be suppressed as compared with a case where light is incident from the planar portion of the outer circumferential surface
Implementation Method 2
unrequired light of a higher-order mode propagating through the core facing the first outer circumferential surface may be attenuated by the influence of the first outer circumferential surface
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A multicore fiber (1) includes a plurality of cores (10) and a cladding (20), in which an outer circumferential surface of the cladding (20) includes a first outer circumferential surface (21) that is a part in a circumferential direction and a second outer circumferential surface (22) that is another part in the circumferential direction, and the first outer circumferential surface (21) bulges outward with a curvature radius larger than that of the second outer circumferential surface (22).