Multimode Fiber Coupler for Multi-Clad Fibers
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Solution Overview
Problem
Current coupling methods for injecting pump fiber optical power into double-clad fibers face inefficiencies in brightness conservation and geometry constraints, particularly in side-pumping approaches, which result in significant power loss and limited flexibility for multi-pump configurations.
Innovation Solution
A coupler design where tapered pump fibers are laterally fused to a multi-clad fiber with varying degrees of fusion, minimizing tapering of the double-clad fiber to preserve its properties and optimizing coupling based on numerical aperture, allowing for efficient power transfer while reducing residual pump power in output fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If tapered fiber bundles are used for end-pumping, then brightness conservation is improved, but device complexity and geometry constraints increase when signal fibers are required
Solution Approach 1:
The invention separates the pump fiber bundle from the signal fiber, allowing them to be independently optimized. The pump fibers are tapered to achieve brightness conservation, while the signal fiber maintains its original properties, eliminating the geometric constraints that would arise from trying to taper both types of fibers together.
Solution Approach 2:
The signal fiber is extracted from the tapered bundle structure and positioned separately, running through the center of the pump fiber arrangement without being subjected to the same tapering process. This allows the pump fibers to be optimized for brightness conservation independently of the signal fiber requirements.
2Adaptability or versatility
If side-pumping is used to avoid geometry constraints, then adaptability is improved, but brightness conservation deteriorates with significant power loss
Solution Approach 1:
The invention transitions from traditional end-pumping (one-dimensional coupling at the fiber end) to side-pumping (coupling from the lateral direction). The tapered pump fibers are arranged radially around the central signal fiber, with their tapered sections fused to the side of the signal fiber, enabling efficient coupling while maintaining configuration flexibility.
3Power
If multiple pump fibers are combined into a bundle, then power delivery is improved, but manufacturing complexity increases due to tapering requirements
Solution Approach 1:
The pump fibers are processed individually through the tapering process before being assembled into the final bundle configuration. This segmentation of the manufacturing process allows each fiber to be precisely controlled during tapering, reducing overall manufacturing complexity compared to attempting to taper the entire bundle as a single unit.
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 approach enhances brightness efficiency and reduces signal loss, achieving coupling efficiencies comparable to end-pumping while maintaining the advantages of continuous side-pumping, allowing for flexible configurations and improved power transfer into double-clad fibers.
Implementation Method 1
A plurality of tapered pump fibers are coupled laterally to a multi-clad fiber... optimizing coupling based on numerical aperture, allowing for efficient power transfer
Implementation Method 2
A plurality of tapered pump fibers are coupled laterally to a multi-clad fiber... with varying degrees of fusion
Data Source
Figure 1(a)~1(e)
Figure 2(a)~2(b)
Figure 3a~3b
AI summary
A coupler having a structure comprising an untapered multi-clad fiber (18) and a plurality of tapered pump fibers (10, 11, 12, 13, 14, 15), each of the tapered pump fibers comprising a converging tapered portion having an extremity, wherein the converging tapered portions (44) are substantially laterally coupled in a twisting arrangement to the multi-clad fiber such that the extremities of the converging tapered portions are all substantially laterally aligned with a longitudinal location around the multi-clad fiber (18), and wherein the numerical apertures of the pump fibers (10, 11, 12, 13, 14, 15) and of the multi-clad fiber (18) are so adjusted as to provide a desired pump coupling and desired brightness efficiency.