Variable-Section Active Optical Fiber to Limit Pump Leakage
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Solution Overview
Problem
Existing active optical fibers with varying cross-sectional areas face issues such as vignetting, leading to pump radiation leakage and overheating, which limits the maximum achievable power and degrades fiber performance.
Innovation Solution
An active optical fiber design with varying cross-sectional areas and modified reflective cladding sections that reduce pump radiation power, incorporating optical inhomogeneities or higher refractive index materials to manage heat and prevent leakage, ensuring single-mode operation and improved power handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the cross-sectional area of the core and reflective cladding is increased to handle higher pump power, then the maximum achievable output power is improved, but vignetting occurs causing pump radiation leakage and overheating
Solution Approach 1:
The patent applies a tapered fiber design where the cross-sectional area of the core and reflective cladding varies along the length of the fiber. The smaller cross-section at the pump input end gradually transitions to a larger cross-section toward the output end, dynamically adapting the area to the local pump power density requirements and preventing vignetting throughout the fiber length
Solution Approach 2:
The patent modifies the reflective cladding by introducing sections with different refractive indices or absorbing materials at specific locations along the fiber. These local modifications are strategically placed to address pump radiation leakage and overheating issues in specific regions without affecting the overall fiber performance
2Reliability
If the cross-sectional area is increased to reduce nonlinear effects, then beam quality is maintained, but the fiber becomes more susceptible to pump radiation leakage
Solution Approach 1:
The patent introduces localized modifications to the reflective cladding with different refractive indices or absorbing properties at specific positions along the fiber. These local quality changes are designed to prevent pump radiation leakage in specific regions while preserving the overall large cross-sectional area that maintains beam quality and reduces nonlinear effects
3Productivity
If the fiber operates at high pump power to increase output power, then productivity is improved, but the fiber lifespan is reduced due to overheating
Solution Approach 1:
The tapered fiber design dynamically distributes pump power density along the fiber length, with the smaller cross-section at the input end handling high pump power density and the gradually increasing cross-section toward the output end reducing power density. This dynamic adaptation prevents localized overheating and enables sustained high-power operation, extending fiber lifespan while maintaining high productivity
Solution Approach 2:
The patent introduces modified reflective cladding sections with different refractive indices or absorbing materials as intermediary elements that manage heat distribution and prevent pump radiation leakage. These intermediary structures act as thermal and optical buffers, protecting the fiber from overheating damage while enabling high-power operation
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
The design enhances the maximum achievable average and peak power while maintaining beam quality by reducing overheating and nonlinear effects, thus extending the fiber's operational lifespan.
Implementation Method 1
incorporating optical inhomogeneities or higher refractive index materials to manage heat and prevent leakage
Implementation Method 2
a first reflective cladding adjacent to the core and having the refractive index less than the refractive index of the core in order to meet the total internal reflection condition at the core—the first cladding boundary
Implementation Method 3
this radiation is absorbed in the active core of the optical fiber, and provides amplification of the signal propagating in the core
Implementation Method 4
reducing overheating and nonlinear effects, thus extending the fiber's operational lifespan
Data Source
AI summary
The active optical fiber comprises an active core doped with at least one the active element and at least two reflective claddings; the cross-sectional area of the core and the cross-sectional area of the reflective cladding adjacent to the core continuously change along the length of the active optical fiber so that the maximum total area Smax of the cross-sectional area of the core and the reflective cladding is at least twice as large as the minimum total area Smin of the cross-sectional area of the core and the reflective cladding; at least one reflective cladding of said at least two reflective claddings comprises at least one modified section configured to reduce the power of the pump radiation propagating along the fiber in at least one reflective cladding after passing the at least one modified section; the at least one modified section of the reflective cladding is located in that region along the axis of the optical fiber, where the total area Sint of the cross-section of the core and the reflective cladding adjacent to the core satisfies the following condition: 1.5×Smin≤Sint≤Smax. The method for manufacturing the active optical fiber and the optical signal amplifier based on the active optical fiber are also proposed.