Optical Fiber Geometry Measurement Using Rotational Orientation
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Solution Overview
Problem
Existing methods for measuring fiber geometry, particularly multi-mode optical fiber geometries, suffer from poor reproducibility and accuracy due to variations in cleave angle and misalignment, leading to inconsistent measurements when re-cleaving fiber samples.
Innovation Solution
A method involving the rotation of the fiber around its optical axis during measurement using a commercially available transmitted near-field (TNF) apparatus, combined with a geometric model that accounts for non-circularity, cleave angle, and angular misalignment, allows for more accurate and repeatable determination of fiber geometry parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transmitted near-field method is used to measure fiber geometry, then the measurement can be conducted with commercially available equipment, but the measurement reproducibility deteriorates when re-cleaving fiber samples
Solution Approach 1:
The patent applies preliminary action by measuring the cleave angle and misalignment parameters before conducting the fiber geometry measurement. These parameters are determined in advance through a series of measurements at different orientations, and then used to correct the subsequent measurement results, eliminating the need for re-cleaving and improving measurement consistency
Solution Approach 2:
The patent changes measurement parameters by conducting measurements at multiple different orientations (rotations) of the fiber around its optical axis. By analyzing how the measured parameters vary with orientation, the system can separate the effects of cleave angle and misalignment from the actual fiber geometry, thereby improving measurement reproducibility
2Ease of operation
If fiber cleaving is performed to enable measurement, then the fiber can be positioned in the instrument, but the cleave angle variations cause measurement inconsistencies
Solution Approach 1:
The patent implements feedback by using the orientation-dependent measurement data to calculate and determine the cleave angle and misalignment parameters. These determined parameters are then fed back to correct and adjust the fiber geometry measurements, creating a closed-loop system that compensates for cleaving variations
Solution Approach 2:
The patent adds another dimension to the measurement process by introducing rotational orientation as a variable. Instead of taking a single measurement, the system performs measurements while rotating the fiber through different orientations, thereby extracting additional information about cleave angle and misalignment that would be inaccessible in a single-orientation measurement
Data Source
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AI summary
A method for testing optical fibers includes using an optical testing instrument to measure a characteristic, such as clad non-circularity, of an optical fiber at a multiple angles of rotation of an optical fiber around its optical axis. From the measurements data points indicative of measured values of the characteristic at the respective angles of rotation are generated. A model is created of the optical fiber having the characteristic as a variable parameter, and from the model a functional relationship between an expected measured value of the characteristic and the angle of rotation and the variable parameter is generated. By varying the parameter a fit of the functional relationship to the data points is made according to one or more predetermined criteria, such as least-squares fit. The value of the characteristic can be found based on the fit. Instrumental parameters, such as fiber misalignment and cleave angle, can also be ascertained by the method.