Multimode Fiber Selection Using Mode Group Delay
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Solution Overview
Problem
There is a need for a method to select multimode optical fibers that are likely to meet bandwidth requirements at a second wavelength based on Differential Mode Delay (DMD) measurements performed at a first wavelength, as performing measurements at the second wavelength on every fiber is not cost-effective, especially for fibers that may not meet the higher OM5 standards.
Innovation Solution
The method involves measuring DMD data at a first wavelength, transforming it into mode group space to obtain relative mode group delay data, and applying specific criteria to select fibers that are likely to meet the bandwidth requirements at the second wavelength, using masks and threshold values to filter the data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DMD measurements are performed at the second wavelength (953 nm) on every fiber to verify OM5 compliance, then measurement accuracy and reliability are improved, but measurement time and cost increase significantly
Solution Approach 1:
The patent performs preliminary DMD measurements at the first wavelength (850 nm) to obtain mode group delay data before final selection. This preliminary measurement allows calculation of predicted bandwidth at the second wavelength, enabling pre-screening of fibers that are likely to meet OM5 requirements before committing to expensive and time-consuming measurements at 953 nm.
Solution Approach 2:
The patent creates a predictive model that copies the relationship between mode group delays and bandwidth performance from the first wavelength to the second wavelength. By using the measured mode group delay data at 850 nm to predict 953 nm bandwidth performance, the system avoids direct measurement at the second wavelength while maintaining selection accuracy.
2Measurement precision
If DMD measurements are performed at the second wavelength (953 nm) on every fiber to verify OM5 compliance, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The system performs preliminary screening at 850 nm using DMD measurements to identify fibers with mode group delay characteristics that predict OM5 compliance. This pre-screening approach maintains measurement precision for the final selection while dramatically increasing throughput by avoiding unnecessary measurements at 953 nm.
Solution Approach 2:
The patent changes the measurement parameter from direct bandwidth measurement at 953 nm to mode group delay measurement at 850 nm, which can be used to predict 953 nm performance. This parameter substitution maintains the ability to accurately identify compliant fibers while improving measurement efficiency.
3Productivity
If all fibers meeting OM4 requirements are selected without additional filtering, then productivity is improved, but measurement precision for OM5 compliance deteriorates
Solution Approach 1:
The patent applies a specific criterion focused on the mode group delay of the lowest-order mode group (LP01 or HE11), which has a different wavelength dependence compared to higher-order modes. By specifically examining this mode's delay characteristics at 850 nm and comparing against a relaxed threshold, the system locally targets the parameter that best predicts OM5 compliance at 953 nm.
Solution Approach 2:
The system changes from verifying bandwidth directly at 953 nm to using mode group delay at 850 nm as a predictive parameter. This parameter transformation allows rapid screening while maintaining the precision needed to identify fibers that will meet OM5 requirements at the second wavelength.
Data Source
AI summary
A method is used to select a multimode fiber meeting requirements of a first minimum bandwidth at a first wavelength and a second minimum bandwidth at a second wavelength different from the first wavelength. Differential mode delay (DMD) data is measured for the multimode fiber at the first wavelength. The DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the first wavelength. The DMD data is transformed into mode group space, to obtain relative mode group delay data as a function of mode group. The multimode fiber is selected based on meeting requirements of the first minimum bandwidth at the first wavelength based on a first set of criteria, comprising a first criterion using as input the measured differential mode delay (DMD) data for the multimode fiber measured at the first wavelength. The multimode fiber is selected based on meeting requirements of the second minimum bandwidth at the second wavelength based on a second set of criteria, comprising: a second criterion using as input the relative mode group delay data. A related system is also described.