Large Effective Area Single Mode Fiber Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical fibers used in high-capacity and long-distance transmission systems face challenges in reducing nonlinear effects while maintaining a balance between effective area, cutoff wavelength, and bending performance, as increasing the mode field diameter to enhance effective area can adversely affect other performance parameters.
Innovation Solution
The optical fiber design features a core layer with a first and second sub core layer, an intermediate cladding layer, and a depressed cladding layer, with specific refractive index differences and radial widths to optimize the effective area and maintain a low cutoff wavelength, thereby improving bending performance and reducing nonlinear effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the mode field diameter is increased to enlarge the effective area, then the nonlinear effects are reduced, but the cutoff wavelength increases and bending performance deteriorates
Solution Approach 1:
The core layer is divided into a first sub core layer and a second sub core layer with different refractive index differences. This segmentation allows independent optimization of mode field distribution and cutoff wavelength characteristics, enabling large effective area while maintaining good bending performance through the first sub core layer's smaller refractive index difference.
Solution Approach 2:
Different regions of the optical fiber structure are assigned different refractive index characteristics. The first sub core layer has a smaller refractive index difference for mode field control, while the second sub core layer has a larger refractive index difference for cutoff wavelength control, achieving local optimization of conflicting requirements.
2Object-generated harmful factors
If the mode field diameter is increased to enlarge the effective area, then the nonlinear coefficient is reduced, but the value of MAC increases and bending performance is adversely affected
Solution Approach 1:
The segmented core structure enables independent control of mode field diameter (through the first sub core layer) and cutoff wavelength (through the second sub core layer), allowing reduction of nonlinear effects via larger MFD while maintaining acceptable bending performance through controlled MAC value.
Solution Approach 2:
By changing the refractive index difference parameters of different core layers, the patent achieves optimal balance between mode field diameter and cutoff wavelength, thereby reducing nonlinear effects while maintaining bending performance.
3Reliability
If a depressed cladding layer is added to inhibit deterioration of bending performance, then the bending performance is improved, but the cutoff wavelength increases
Solution Approach 1:
The core layer is segmented into two sub core layers with different refractive index characteristics, allowing the first sub core layer to control mode field for bending performance while the second sub core layer controls cutoff wavelength, avoiding the need for depressed cladding layer that would increase cutoff wavelength.
Solution Approach 2:
The intermediate cladding layer acts as a mediator between the dual-sub core structure and the outer depressed cladding layer, enabling the core structure to achieve both bending performance and cutoff wavelength control without relying solely on the depressed cladding layer volume.
Data Source
AI summary
A single-mode fiber with a large effective area comprises a core layer and a cladding layer. The core layer is cladded with an intermediate cladding layer, and a depressed cladding layer is provided outside the intermediate cladding layer. The core layer comprises a first fiber sub core layer having a radius r1 of 1.5-5 μm and a relative refractive index difference Δn1 of 0.05-0.22%, and a second sub core layer having a unilateral radial width (r2−r1) of 1.5-5 μm and a relative refractive index difference Δn2 of 0.15-0.34%, where Δn1 is less than Δn2. Accordingly, the optical fiber can reach an effective area equal to or greater than 120 μm2 when the related parameters thereof are optimized.