Bridge Optical Fiber for Thermal Management in Double-Clad Amplifiers
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Solution Overview
Problem
Optical fiber amplifiers and lasers face challenges in scaling output power due to adverse thermal effects caused by pump light absorption, particularly in thulium-doped systems, which lead to heat generation and potential fiber damage, limiting power scaling and efficiency.
Innovation Solution
The introduction of a bridge optical fiber with a specific refractive index profile that reduces the initial overlap of pump radiation with the active core, spreading heat generation along a longer length of the active optical fiber, thereby reducing thermal stress and increasing the damage power threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pump radiation is directly coupled to the active optical fiber to maximize pump absorption, then pump absorption efficiency is improved, but thermal effects and heat generation increase causing fiber damage
Solution Approach 1:
A bridge optical fiber is introduced as an intermediary component between the pump source and the active optical fiber. This bridge fiber has a specific refractive index profile that reduces the initial overlap of pump radiation with the active core, thereby mediating the energy transfer to reduce thermal effects while maintaining pump absorption efficiency.
Solution Approach 2:
The optical path is segmented into multiple sections: a pump section of the active optical fiber with reduced pump absorption and a signal section with normal pump absorption. This segmentation allows the pump absorption to be distributed along the fiber length, reducing localized heat generation while maintaining overall efficiency.
2Device complexity
If the pump absorption is uniformly distributed along the active optical fiber, then simplicity is maintained, but thermal stress concentrates in specific regions limiting power scaling
Solution Approach 1:
The active optical fiber is designed with different local properties: the pump section has a refractive index profile optimized for reduced pump absorption, while the signal section has a profile for normal operation. This local differentiation allows thermal management in the pump section while maintaining performance in the signal section.
Solution Approach 2:
The pump absorption characteristics are made dynamic along the fiber length, with the pump section having reduced absorption and the signal section having normal absorption. This dynamic distribution allows the system to manage thermal stress while maintaining overall 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 approach allows for increased pump absorption and gain along the active optical fiber while minimizing heat generation in the initial segment, enabling higher power scaling without exceeding the fiber's damage threshold.
Implementation Method 1
The bridge optical fiber includes an inner core configured to guide radiation of the active wavelength, the inner core having an inner core active wavelength refractive index profile and an inner core pump wavelength refractive index profile
Implementation Method 2
rare earth materials disposed in the core of an active optical fiber absorb pump radiation of a predetermined wavelength, and, in response, provide or amplify light of a different wavelength for propagation in the core
Implementation Method 3
the well-known erbium-doped fiber amplifier receives pump radiation having a wavelength of 980 or 1480 nm, and amplifies optical radiation propagating in the core and having a wavelength of about 1550 nm
Implementation Method 4
one or more outer claddings surrounding the pump cladding and configured to guide radiation of a pump wavelength within the pump cladding and the core
Data Source
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AI summary
The present disclosure relates to systems and methods for reducing thermal effects in double- clad optical fiber amplifying systems via control of the pump absorption. One optical fiber amplifying system for reducing thermal effects includes one or more first optical pump sources, each configured to output radiation of a pump wavelength, a bridge optical fiber, hav ing an input configured to recei v e the radiation of the pump wavelength output by the one or more first optical pump sources and an output, and an active optical fiber that has a first end subsianiially directly coupled to the output of the bridge optical fiber and a second end. The active optical fiber is configured to amplify radiation of the first active wavelength when pumped with radiation of the pump wavelength.