Birefringence Axis Determination in Polarization-Maintaining Optical Fiber
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Solution Overview
Problem
Existing methods for determining the birefringence axis of polarization-maintaining optical fibers, such as side viewing and end viewing techniques, face limitations in accuracy due to image defects and user input errors, particularly in fibers with poor contrast and dynamic range issues.
Innovation Solution
A method involving image processing techniques, including local image equalization and Hough space analysis, to accurately determine the birefringence axis by constructing edge maps and calculating the center positions of birefringence-defining structures on the fiber end face, allowing for precise alignment and splicing of optical fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If end viewing technique is used to determine birefringence axis, then measurement can be performed on fiber end face, but accuracy is compromised due to end face artifacts, poor contrast, and lack of dynamic range in imaging sensor
Solution Approach 1:
The patent converts the harmful effect of end face artifacts and poor contrast into a benefit by applying image processing techniques. Specifically, it uses image equalization to enhance contrast and dynamic range, and employs feature detection algorithms that can identify birefringence-defining features despite the presence of artifacts. This transforms the previously unusable end face images into accurate measurement data.
Solution Approach 2:
The patent introduces image processing algorithms as intermediaries between the imaging sensor and the measurement system. These algorithms include image equalization to enhance contrast, edge detection to identify features, and Hough transform to determine the birefringence axis. The intermediaries process the degraded images into usable measurement data, eliminating the need for direct visual interpretation of the artifact-ridden images.
2Measurement precision
If side viewing technique is used to determine birefringence axis, then internal fiber structure can be imaged, but accuracy is limited because the technique does not directly measure the fiber's internal structure
Solution Approach 1:
The patent creates a digital copy of the fiber end face through imaging, then applies image processing algorithms to enhance and analyze this copy. The Hough transform algorithm processes the image data to accurately determine the birefringence axis by identifying the orientation of birefringence-defining features. This copying and processing approach enables precise measurement without requiring direct physical access to the internal structure.
3Adaptability or versatility
If user input is required for position and size parameters of birefringence axis defining features, then system can accommodate various fiber types, but user input errors compromise system performance
Solution Approach 1:
The patent implements self-service functionality where the system automatically determines fiber parameters without requiring user input. The image processing algorithms automatically identify the fiber core position, calculate the birefringence axis orientation, and determine feature dimensions. The system uses the Hough transform to automatically detect the orientation of birefringence-defining features and computes the birefringence axis based on the image data alone, eliminating user input errors while maintaining versatility across fiber types.
Data Source
AI summary
In some embodiments, a non-transitory processor-readable medium storing code includes code to cause a processor to receive an image signal associated with an image of an end face of a polarization-maintaining optical fiber (PM fiber), determine a center position of the PM fiber, perform a local image equalization on the end face, and define an edge map of the end face. The code can perform a Hough space analysis on the edge map to determine the center position of a first structure and/or a second structure on the end face. The first structure and the second structure can each define at least in part a birefringence of the PM fiber. A birefringence axis of the PM fiber can be calculated based on at least two of the center position of the PM fiber, the center position of the first structure and the center position of the second structure.