Azimuthal Multicore Fiber Splicing for Core Assignment Alignment
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Solution Overview
Problem
Existing methods struggle to accurately align rotationally non-invariant optical fibers, leading to suboptimal insertion loss and polarization extinction ratio due to misalignment of core regions and asymmetries, particularly in multicore fibers with small mode field diameters.
Innovation Solution
An azimuthal alignment apparatus and methodology that uses an additive component approach to identify critical features for precise alignment, distinguishing between core regions and secondary features, and adjusts fiber positions before fusion splicing to minimize misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional profile alignment system is used for rotationally non-invariant fibers, then alignment process is simplified, but alignment precision deteriorates due to inability to achieve accurate azimuthal alignment
Solution Approach 1:
The alignment process is segmented into two distinct phases: a rough alignment phase using the profile alignment system to establish basic transverse positioning, followed by a fine azimuthal alignment phase using image processing of end-face views to precisely rotate and position the fiber. This segmentation allows each phase to optimize for its specific requirement without interfering with the other.
Solution Approach 2:
The profile alignment system performs preliminary transverse alignment before the azimuthal alignment step. By pre-positioning the fiber ends in approximate alignment, the subsequent azimuthal alignment operation only needs to make fine rotational adjustments, improving both efficiency and precision of the final alignment.
2Manufacturing precision
If all transverse features are aligned in rotationally non-invariant fibers, then feature alignment is optimized, but core alignment deteriorates due to conflicting alignment requirements of different features
Solution Approach 1:
The image processing algorithm applies different alignment priorities to different regions of the fiber end-face image. The core region is identified and given highest priority for alignment, while other features such as cladding boundaries or coating patterns are aligned with lower priority or used only for verification. This local differentiation resolves conflicts between competing alignment features.
Solution Approach 2:
The invention explicitly handles the asymmetric nature of rotationally non-invariant fibers by implementing azimuthal rotation capability. Unlike symmetric fibers where any rotation maintains alignment, asymmetric fibers require precise angular positioning. The system detects the asymmetric features in the image and calculates the specific rotation angle needed to achieve optimal core alignment, then applies that precise rotation.
3Reliability
If fiber endfaces are positioned at optimal splicing gap, then fusion splicing quality is improved, but alignment adjustment range deteriorates due to limited space for azimuthal alignment operations
Solution Approach 1:
The system performs azimuthal alignment operations before the fiber endfaces are positioned at the optimal splicing gap. The fiber is first brought into approximate transverse alignment, then azimuthal rotation and fine positioning are completed while the fiber is still accessible. Only after alignment is achieved does the system advance the fiber to the final splicing position, ensuring both adequate adjustment range and optimal splicing quality.
Solution Approach 2:
The invention separates the alignment operations in the longitudinal dimension from the transverse and azimuthal alignment operations. By performing alignment in the transverse and azimuthal dimensions first, while keeping the longitudinal gap larger, the system gains mechanical access and adjustment range. The longitudinal positioning is then optimized separately for splicing quality without compromising the previously achieved alignment.
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
Achieves accurate alignment of rotationally non-invariant fibers, reducing splice loss and signal variations in transmission systems by ensuring optimal core-to-core alignment and compensating for fabrication imperfections and asymmetries.
Implementation Method 1
the fibers including their cores are fused together by an electric arc discharge
Data Source
AI summary
A system of aligning concatenated sections of multicore optical fiber incorporates the capability of intentionally changing core assignments as part of the azimuthal alignment process. The intentional changing of core assignments, referred to as offset clocking, compensates for differences in properties of the individual core regions in a way that reduces variations between the spatial channels supported in the transmission system. The offset clocking technique can be used, e.g., to improve the attenuation (or other selected properties of the propagating signals). The offset clocking technique may be used to step through sequential changes core assignments at one or more splice locations (passive clocking) or identify a particular pairing of cores from one fiber section to the next (e.g., “good quality” core assigned to a “poor quality” signal exiting the first section) and rotate the fiber sections with respect to each other to achieve this particular core assignment.