Multimode Fiber Core Cane Classification for Bandwidth Prediction
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Solution Overview
Problem
Existing optical fiber preform characterization techniques do not provide adequate metrics to optimize the selection of preforms for manufacturing multimode fibers that conform to OM standards, leading to significant variations in effective modal bandwidth.
Innovation Solution
A method for classifying core canes by determining a relative refractive index profile, fitting it to an alpha profile, generating a non-alpha residual profile, and computing metrics such as Δdiff-sum, Δdiff-max, and τerr to predict the bandwidth of the resulting optical fiber, allowing for selection or discard of preforms based on these metrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing optical fiber preform characterization techniques are used, then manufacturing process is simple, but manufacturing precision of refractive index profile is insufficient leading to substantial variation in EMB
Solution Approach 1:
The patent applies preliminary action by measuring and analyzing the refractive index profile of the core cane before the fiber drawing process. This allows identification and selection of core canes with optimal refractive index profiles prior to manufacturing, enabling prediction of bandwidth performance and selection of preforms that will produce fibers meeting OM standards, thereby improving manufacturing precision without adding complexity to the actual drawing process
Solution Approach 2:
The patent replaces traditional mechanical/physical measurement methods with optical measurement techniques. By using light propagation characteristics to measure the refractive index profile through the core cane, the method achieves high precision characterization without complex mechanical intervention, substituting optical field interactions for traditional measurement approaches
2Productivity
If all preforms are processed into optical fibers, then productivity is maximized, but loss of time increases due to testing and sorting after manufacturing
Solution Approach 1:
The patent performs preliminary characterization of core canes before fiber drawing, measuring refractive index profiles and calculating bandwidth metrics in advance. This allows sorting and selection of qualifying preforms before the time-consuming fiber drawing and testing processes, reducing waste and avoiding unnecessary processing of non-compliant materials, thereby improving productivity while reducing overall time loss
Solution Approach 2:
The patent extracts the characterization and selection step from the later testing phase and moves it to the beginning of the process. By taking out the refractive index profile measurement and bandwidth prediction activities and performing them on core canes before drawing, the method eliminates the need for subsequent bandwidth testing and sorting of finished fibers, reducing time loss and improving productivity
3Manufacturing precision
If refractive index profile measurement precision is increased, then manufacturing precision improves, but measurement precision requirements become more demanding
Solution Approach 1:
The patent substitutes optical measurement methods for traditional measurement techniques. By using light propagation and analyzing optical characteristics to determine the refractive index profile, the method achieves high measurement precision through optical field interactions rather than mechanical or electrical measurement systems, meeting demanding accuracy requirements while maintaining practical implementation
Solution Approach 2:
The patent applies a universal optical measurement approach that can characterize the refractive index profile across different core cane types and manufacturing conditions. The method uses fundamental optical principles that are applicable regardless of specific material composition or geometric variations, providing consistently high measurement precision across diverse scenarios without requiring specialized measurement systems for each case
Data Source
AI summary
Methods for classifying a core cane of an multimode optical fiber are disclosed. In embodiments, the method includes determining a relative refractive index profile Δ(r) of the core cane; fitting the relative refractive index profile Δ(r) to an alpha profile Δfit(r) defined by:Δfit(r)=Δo,fit(1-(rafit)αfit)where Δo,fit is a relative refractive index at a longitudinal centerline of the core cane, αfit is a core shape parameter, and afit is an outer radius of the core cane; generating a non-alpha residual profile Δdiff(r)=Δ(r)−Δfit(r) for the core cane; computing one or more metrics from Δdiff(r), and using the one or metrics in a classification of the core cane, the classification comprising a prediction of whether a bandwidth at a pre-determined wavelength of an optical fiber drawn from a preform comprising the core cane exceeds a pre-determined bandwidth at the pre-determined wavelength.