Variable Bend Fiber Launch Control for Optical Measurement Precision
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Solution Overview
Problem
Existing methods for controlling launch conditions in optical network test and measurement applications, such as mandrel wrapping, fail to provide consistent and precise mode group launch, leading to significant variations in fiber attenuation measurements, especially with different light sources and multimode fiber sizes, and do not meet emerging standards like Encircled Flux (EF) requirements, while also being cumbersome and heavy.
Innovation Solution
A linear variable mandrel with adjustable bend points and a dual-wavelength combiner system using step index fiber, combined with a mode scrambler, allows for precise control of launch conditions by adjusting the fiber bend and modal distribution, reducing variability and size while meeting EF standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mandrel wrapping is used to control launch conditions, then higher order modes are stripped out, but measurement consistency varies by up to 50% between different light sources
Solution Approach 1:
The patent applies parameter changes by transitioning from fixed mandrel wrapping to variable bend radius control. The mode condition controller allows continuous adjustment of the bend radius parameter, enabling optimization for different light sources and fiber types. This variable parameter approach replaces the fixed geometric constraint of traditional mandrels with a tunable bend radius that can be adjusted to achieve consistent Encircled Flux measurements across different sources.
Solution Approach 2:
The invention implements dynamics by making the bend radius adjustable and variable rather than fixed. The mode condition controller provides dynamic control over the fiber bend characteristics, allowing the system to adapt to different launch conditions requirements. This dynamic adjustment capability enables the system to maintain measurement consistency across varying light source characteristics and fiber configurations.
2Device complexity
If fixed diameter mandrel is used, then device structure is simple, but it cannot accommodate different multimode fiber sizes and wavelengths
Solution Approach 1:
The patent achieves universality by designing a mode condition controller that can handle multiple fiber sizes (50μm, 62.5μm) and wavelengths (850nm, 1300nm) with a single device. The variable bend radius mechanism allows the same apparatus to be optimized for different fiber types and wavelength combinations, eliminating the need for multiple fixed-diameter mandrels for different applications.
Solution Approach 2:
The invention uses dynamic adjustment of the bend radius to accommodate different fiber sizes and wavelengths. By making the bend radius variable rather than fixed, the device can be tuned to work with 50μm fiber at 850nm, 62.5μm fiber at 1300nm, and other combinations, providing multi-functionality without increasing fundamental device complexity.
3Measurement precision
If multiple wraps of fiber around mandrel are used, then launch condition control is achieved, but device height increases due to stacking effect
Solution Approach 1:
The patent applies dimensionality change by transitioning from a vertical stacking configuration to a horizontal or planar layout. Instead of wrapping fiber multiple times around a mandrel which stacks vertically, the invention uses a variable bend radius mechanism that achieves the same mode control function in a different spatial arrangement, reducing the vertical height dimension while maintaining launch condition control capability.
Solution Approach 2:
The invention extracts the essential function of mode control from the traditional mandrel wrapping geometry. By separating the bend induction function from the fixed circular mandrel structure, the system achieves mode control without requiring multiple wraps and the associated vertical stacking, thereby reducing device height while preserving the core functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables reproducible and accurate launch conditions, reducing measurement inconsistencies by up to 50% and meeting stringent standards, while also reducing the size and weight of the equipment, making it easier to use and manufacture.
Implementation Method 1
A fiber bending apparatus provides an adjustable bend point to a fiber, whereby adjustment of the bend amount enables adjustment of the launch conditions to a desired amount
Data Source
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AI summary
A system, apparatus and method for providing controlled launch conditions to an optical light source comprises adjustable fiber bending/deforming apparatus to allow adjustment of the device such that multimode launch conditions can be accurately controlled. Both LED light source and OTDR/laser implementations are provided.