Optical Fiber Mode Field Diameter from Near-Field Variational Analysis
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Solution Overview
Problem
Existing methods for calculating mode field diameter (MFD) in multi-mode and multi-mode multi-core fibers are inaccurate due to discrepancies between actual electric field distributions and ideal Gaussian modes, leading to errors in connection loss estimation.
Innovation Solution
A device and method using a mathematical expression based on a variational expression of a propagation constant derived from a wave equation to accurately determine MFD from near field patterns, incorporating a near field pattern acquisition unit and a mode field diameter acquisition unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the MFD is calculated using the Gaussian mode approximation formula (Expression 1), then the calculation is simple and quick, but the accuracy deteriorates when the actual electric field distribution deviates from the ideal Gaussian mode
Solution Approach 1:
The patent changes the mathematical parameter used for MFD calculation from the Gaussian mode approximation (Expression 1) to a variational expression based on the wave equation (Expression 2). This parameter change allows accurate calculation even when the actual electric field distribution deviates from the ideal Gaussian mode, resolving the contradiction between calculation simplicity and accuracy.
Solution Approach 2:
The patent replaces the empirical Gaussian approximation method with a theoretical variational expression derived from the wave equation. This substitution transforms the calculation from a simplified model-based approach to a fundamental physics-based approach, improving accuracy without requiring complex measurements.
2Reliability
If the MFD is calculated using the variational expression from the wave equation, then the connection loss deduction accuracy is improved, but the calculation complexity increases
Solution Approach 1:
The variational expression (Expression 2) is derived from the wave equation itself, making the calculation self-contained and physically fundamental. The method uses the near field pattern directly without requiring external approximation models, allowing the system to serve itself by extracting MFD information directly from the physical field distribution.
Solution Approach 2:
The patent introduces the variational expression as an intermediary mathematical tool that bridges the near field pattern and the MFD. This intermediary allows accurate extraction of MFD information from the actual electric field distribution without requiring direct complex measurements or approximations.
Data Source
AI summary
The mode field diameter acquisition device according to the present disclosure is a device for acquiring a mode field diameter of each spatial mode of an optical fiber having a core, through which a plurality of spatial modes can propagate, from a near field pattern, and includes a mode field diameter acquisition unit configured to acquire a mode field diameter of a freely-selected spatial mode using a near field pattern of the spatial mode, and a mathematical expression based on a variational expression of a propagation constant of the spatial mode.