Multi-Core Fiber Evaluation for Connection Loss Using Core Spacing
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Solution Overview
Problem
Existing methods for evaluating multi-core optical fibers, which have multiple cores in the clad, are limited to assessing the deviation between the center of the clad and the center of the core, and cannot account for variations in core spacing due to changes in clad diameter, leading to potential connection losses that do not meet desired specifications.
Innovation Solution
An evaluation method and device that approximates the clad as a circle and measures center coordinates of each core, determining if the length and angle between cores fall within predetermined ranges to ensure a desired connection loss characteristic, using equations to define these ranges based on mode field diameter and core spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing evaluation methods (NPLs 3 and 4) are used to assess multi-core fiber, then the deviation between center of clad and center of core can be evaluated, but the method cannot account for variations in core spacing due to changes in clad diameter, leading to connection loss issues
Solution Approach 1:
The invention changes the evaluation parameters from single-point center deviation to multi-parameter assessment including core-to-core distance and relative positional relationships. By evaluating multiple structural parameters simultaneously, the method accounts for clad diameter variations and their impact on connection loss, thereby improving reliability while maintaining measurement precision.
Solution Approach 2:
The invention transitions from one-dimensional center deviation assessment to two-dimensional relative position evaluation between multiple cores. By considering the spatial relationships and distances between core centers in addition to clad center deviation, the method captures the full impact of structural variations on connection performance.
2Loss of energy
If core arrangement is ideal with fixed spacing, then connection loss can be minimized, but clad diameter tolerance causes core spacing variations that increase connection loss
Solution Approach 1:
The invention performs preliminary evaluation of core positions and spacings before connection to predict potential connection loss. By assessing the relative positional relationships and calculating expected connection performance in advance, the method allows for pre-screening and selection of fibers that will meet connection requirements, compensating for manufacturing tolerances.
Solution Approach 2:
The invention uses measured core positions and spacings as feedback to evaluate whether the fiber meets connection requirements. The evaluation method provides feedback on the actual structural parameters versus ideal parameters, enabling quality control and selection of fibers that will achieve desired connection loss specifications despite manufacturing variations.
3Reliability
If detailed structural parameter evaluation is performed for each core, then connection loss can be accurately predicted, but the evaluation complexity increases significantly
Solution Approach 1:
The invention creates a universal evaluation method that can assess multi-core fiber structures with different numbers of cores and configurations using the same basic approach. The method evaluates relative positional relationships and distances between cores, which applies universally regardless of the specific fiber design, thereby maintaining reliability without requiring complex specialized procedures for each fiber type.
Solution Approach 2:
The invention segments the evaluation into distinct measurable parameters: core-to-core distances, relative positional relationships, and their relationships to clad diameter. By breaking down the complex evaluation into these separable components, the method achieves accurate connection loss prediction through systematic measurement of individual parameters rather than attempting to assess the entire structure as a single complex entity.
Data Source
AI summary
An object of the present invention is to provide an evaluation method and an evaluation device for easily determining whether or not a structural parameter of a multi-core fiber satisfies a desired connection loss value (a specification).The evaluation method according to the present invention includes a step of measuring center coordinates of each core with the center coordinates when a clad is approximated by a circle as an origin in an observed cross-sectional structure of the multi-core fiber to be objected, obtaining a length of a line segment connecting the origin and the center of each core and an angle formed by two line segments connecting the origin and two adjacent cores, and judging whether or not a desired connection loss characteristic is satisfied on the basis of whether or not the values satisfy a predetermined determination formula.