Multi-core fiber amplifier with reduced-diameter excitation path
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Solution Overview
Problem
Existing optical fiber amplifiers face issues with mode coupling, where longer wavelengths used for optical signals lead to inter-core crosstalk and reduced amplification efficiency, and structures that attempt to mitigate this often result in inefficient power concentration of excitation light.
Innovation Solution
The optical fiber amplifier design includes a third optical fiber with a reduced-diameter portion where the distance between cores is shorter, allowing excitation light to be mode-coupled between cores, thereby suppressing mode coupling of optical signals and ensuring uniform power distribution, which reduces the number of laser diodes needed and enhances amplification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If excitation light is applied to a rare-earth-doped multi-core fiber with constricted cores to accelerate mode coupling, then amplification speed increases, but inter-core crosstalk increases due to longer wavelength of optical signals
Solution Approach 1:
The patent divides the excitation light transmission path from the signal amplification path by using separate optical fibers. The excitation light is transmitted through a dedicated third optical fiber with constricted cores to outer cores, while the signal transmission occurs through the second optical fiber with rare-earth doping. This segmentation prevents inter-core crosstalk between excitation light and signal light while maintaining efficient mode coupling for excitation light distribution.
Solution Approach 2:
The patent introduces a third optical fiber as an intermediary component that carries excitation light separately from the signal-carrying second optical fiber. This intermediary fiber with constricted cores enables efficient mode coupling and excitation light distribution without directly interacting with the signal transmission path, thereby eliminating harmful inter-core crosstalk while maintaining amplification efficiency.
2Adaptability or versatility
If multi-mode excitation light enters the cladding of a rare-earth-doped MCF to collectively excite all cores, then all cores are excited simultaneously, but power concentration of excitation light becomes inefficient
Solution Approach 1:
The patent applies local quality by creating a reduced-diameter portion in the third optical fiber where only specific regions have constricted cores. This localized constriction enables efficient mode coupling and power concentration of excitation light from the central core to outer cores, while maintaining the ability to collectively excite all cores through the third optical fiber's structured design.
3Productivity
If the distance between cores in the excitation light fiber is reduced to enable mode coupling, then excitation light distribution improves, but the fiber structure becomes more complex
Solution Approach 1:
The patent implements preliminary action by pre-structuring the third optical fiber with a reduced-diameter portion that has constricted cores before excitation light enters. This pre-configured structure with varying core distances enables automatic mode coupling and efficient excitation light distribution without requiring real-time control or complex dynamic adjustments, simplifying the overall system while maintaining high distribution efficiency.
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 design efficiently amplifies optical signals by suppressing mode coupling and ensuring uniform excitation light distribution, leading to improved amplification efficiency and reduced connection loss between fibers.
Implementation Method 1
the excitation light entering from the excitation light source to one of the third cores is mode-coupled with another core of the third cores to distribute the excitation light in the reduced-diameter portion
Implementation Method 2
The second optical fiber has a plurality of second cores and a cladding surrounding the plurality of second cores, in which a rare-earth element is doped to the second optical fiber. The second optical fiber is configured to amplify the optical signal propagating therein by excitation light.
Data Source
AI summary
An optical fiber amplifier comprising a first optical fiber, a second optical fiber, a third optical fiber, and an excitation light source, is disclosed. Each optical fiber has cores and a cladding surrounding the cores. The third optical fiber transmits excitation light used for signal amplification in the second optical fiber. A rare-earth element is doped to the second optical fiber that amplifies an optical signal propagating therein by the excitation light. The third optical fiber includes a reduced-diameter portion. A distance between the cores of the third optical fiber in the reduced-diameter portion is shorter than a distance between the cores in other portion of the third optical fiber, and the excitation light entering from the excitation light source to one of the cores of the third optical fiber is mode-coupled with another core of the third optical fiber to distribute the excitation light in the reduced-diameter portion.