Fourier Series Interrelation Profile Analysis for Polarization-Maintaining Fiber Alignment
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Solution Overview
Problem
Current methods for aligning polarization-maintaining optical fibers, such as the interrelation profile alignment (IPA) method, face limitations including requiring similar fiber types, preloaded IPA profiles, and inability to automatically correct asymmetrical structures, especially for new specialized fibers used in advanced applications.
Innovation Solution
The method employs a Fourier series expansion to generate interrelation profile analysis (IPA) profiles, allowing for the analysis of PM optical fibers without preloaded profiles, enabling automatic corrections for asymmetrical structures, and aligning fibers without the need for a polarization extinction ratio (PER) meter, using a system with a light source, fiber rotating unit, and IPA profile calculating unit to determine points of symmetry based on Fourier series profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional interrelation profile alignment (IPA) method is used, then alignment can be performed for conventional PM fibers, but it cannot handle new specialized PM fiber types with asymmetrical structures
Solution Approach 1:
The patent transforms the alignment approach from direct image profile comparison to Fourier domain analysis. By converting spatial domain intensity profiles into frequency domain representations, the system can extract rotational orientation information that is independent of fiber type geometry, enabling universal application across conventional and specialized asymmetrical PM fiber types while maintaining alignment accuracy
Solution Approach 2:
The patent replaces the mechanical/visual alignment system (direct image comparison requiring similar fiber types) with a mathematical signal processing system. The Fourier transform-based method substitutes physical profile matching with frequency domain correlation, which inherently handles asymmetrical structures by extracting rotational characteristics from the frequency spectrum rather than relying on visual profile similarity
2Productivity
If direct correlation method is used, then alignment speed is improved, but it requires preloaded IPA profiles and cannot automatically correct asymmetrical structures
Solution Approach 1:
The patent extracts the essential alignment information (rotational orientation) from the complex intensity profile data by applying Fourier transform. This extraction process separates the critical rotational phase information from the irrelevant profile shape details, eliminating the need for preloaded reference profiles while maintaining fast alignment speed through direct frequency domain correlation
Solution Approach 2:
The patent creates a mathematical model (Fourier series representation) that copies the essential rotational characteristics of any PM fiber type without requiring physical profile databases. This universal mathematical representation allows the system to handle any fiber type through the same correlation algorithm, eliminating device complexity associated with maintaining multiple reference profiles
3Device complexity
If polarization observation by lens effect (POL) method is used, then device simplicity is improved, but measurement precision deteriorates due to obtaining only contrast information
Solution Approach 1:
The patent transitions from analyzing intensity contrast in the spatial domain (POL method) to analyzing frequency domain characteristics through Fourier transform. This dimensional transformation from spatial to frequency domain provides additional information about rotational orientation that is not accessible through simple contrast measurement, thereby improving precision while maintaining the simplicity of using standard intensity detection
Data Source
AI summary
A method of analyzing a polarization-maintaining (PM) optical fiber includes illuminating a side of the PM optical fiber, physically rotating the PM optical fiber and measuring light intensity of light transmitted through the PM optical fiber to obtain an image profile, mathematically shifting the image profile at incremental rotation angles, expanding the image profile at each rotational angle into a Fourier series profile, and determining points of symmetry of the PM optical fiber based on the Fourier series profiles.