Rare Earth Doped Fiber Cavities for Mode Gain Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical fiber amplifiers face challenges in compensating for gain differences between modes without adding new devices, which leads to deterioration of amplification characteristics and increased production costs.
Innovation Solution
A rare earth doped fiber with cavities inside the core is used to reduce gain deviation between modes, achieved by applying loss differently to each mode through strategically placed cavities along the longitudinal direction, formed using a femtosecond laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mode conversion device is added to compensate for gain difference between modes, then amplification characteristics are improved, but device complexity and size increase
Solution Approach 1:
The invention extracts the mode conversion function from a separate external device and integrates it directly into the optical fiber structure through cavities formed within the fiber core. This eliminates the need for external mode conversion devices while maintaining the gain equalization function.
Solution Approach 2:
The invention merges the amplification function and mode conversion function into a single integrated component - the rare earth doped optical fiber with cavities. The cavities serve dual purposes: maintaining the fiber's amplification capability while simultaneously providing mode conversion to equalize gain across different modes.
2Reliability
If refractive index distribution and rare earth doped region are optimized to compensate gain difference, then amplification characteristics are improved, but manufacturing complexity and production cost increase
Solution Approach 1:
The invention introduces cavities with specific local properties (different refractive index regions) at predetermined positions within the fiber core. These localized structural modifications create mode-dependent loss characteristics that equalize gain without requiring complex overall optimization of the entire doped region.
Solution Approach 2:
The cavities are formed in advance during the fiber manufacturing process using techniques like femtosecond laser writing or photonic crystal formation. This preliminary structuring of the fiber core enables automatic mode equalization during operation without requiring complex post-manufacturing adjustments or optimizations.
3Reliability
If external devices are added to compensate gain deviation, then gain compensation is achieved, but loss increases
Solution Approach 1:
The optical fiber itself provides the mode equalization function through its internal cavity structure. The fiber automatically compensates for mode-dependent gain differences through the mode conversion effect created by the cavities, eliminating the need for external active compensation devices that would introduce additional loss.
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
Gain compensation is achieved with a simple configuration, maintaining low noise figure and low loss, thereby improving transmission characteristics without adding external devices.
Implementation Method 1
A difference in loss occurring in the cavity region depending on the modes generates the gain deviation between the modes
Implementation Method 2
a gain medium including a core doped with a rare earth and a cladding region around the core
Data Source
AI summary
An object of the present disclosure is to allow gain compensation with a simple configuration without adding a new device to the outside. The present disclosure discloses a rare earth doped fiber including a core doped with a rare earth and a cladding region around the core, wherein one or more cavities are provided inside the core, and at least one of the cavities are provided along a longitudinal direction of the rare earth doped fiber.