Transmission Optical Fiber Large Effective Area Bending Loss
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Solution Overview
Problem
Existing optical fibers with enlarged effective areas face increased bending and microbending losses, and elevated effective cut-off wavelengths, making them incompatible with standard single-mode fibers and increasing manufacturing costs.
Innovation Solution
An optical fiber profile with a central core, intermediate cladding, and depressed cladding is designed, where the depressed cladding is sufficiently buried and narrow to limit bending and microbending losses while maintaining an effective area of over 120 µm² and ensuring single-mode operation below 1600 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the central core is enlarged and flattened to increase effective area, then non-linear effects are reduced and transmission distance is extended, but bending and microbending losses increase
Solution Approach 1:
The optical fiber is segmented into multiple functional regions: central core, inner cladding, intermediate cladding, and outer cladding. Each region has specific refractive index characteristics that work together to achieve large effective area while controlling bending losses. The intermediate cladding acts as a buffer zone between the core and outer cladding, managing mode propagation and reducing sensitivity to bending.
Solution Approach 2:
Different regions of the optical fiber are assigned different refractive index qualities: the central core has high refractive index for light confinement, the inner cladding has depressed refractive index to control mode field distribution, the intermediate cladding provides transition, and the outer cladding provides overall confinement. This local differentiation allows optimization of each region's function.
2Area of moving object
If the central core is enlarged and flattened to increase effective area, then non-linear effects are reduced, but effective cut-off wavelength increases
Solution Approach 1:
The fiber structure is divided into multiple cladding layers with different refractive index profiles. The intermediate cladding layer specifically controls the cut-off wavelength by providing a refractive index transition that maintains single-mode operation characteristics at standard wavelengths while allowing larger core dimensions.
Solution Approach 2:
The refractive index parameters are carefully optimized: the central core refractive index difference is controlled at 0.3-0.5%, the inner cladding has depressed refractive index, and the intermediate cladding provides gradual transition. These parameter changes enable the fiber to maintain single-mode operation below 1600nm while achieving large effective area.
3Reliability
If a depressed cladding is added to control cut-off wavelength and reduce bending losses, then single-mode operation is maintained, but device complexity increases
Solution Approach 1:
The fiber is segmented into four distinct layers with clearly defined refractive index characteristics. This segmentation provides systematic control over optical properties while maintaining manufacturing feasibility through standardized deposition processes for each layer.
Solution Approach 2:
The intermediate cladding layer serves multiple functions simultaneously: it provides refractive index transition, controls cut-off wavelength, reduces bending loss sensitivity, and maintains mode field distribution. This multi-functionality reduces the need for additional specialized components or structures.
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 optical fiber achieves an enlarged effective area with equivalent or reduced bending and microbending losses compared to standard single-mode fibers, maintaining single-mode character in the C band and minimizing manufacturing costs.
Implementation Method 1
an optical fiber profile comprising a central core, an intermediate cladding and a buried or depressed cladding
Implementation Method 2
the refractive index profile is generally qualified in relation to the graph plotting the function relating the refractive index with the optical fiber radius
Data Source
Figure 1
AI summary
The present invention relates to a transmission optical fiber comprises a central core having a radius (r1) larger than or equal to 5.5 µm and a refractive index difference (Δn1) less than or equal to 5.0.10-3; an intermediate cladding having a radius (r2) and a refractive index difference (Δn2), the width of the intermediate cladding (r2-r1) being more than 5 µm; and a depressed cladding having a radius (r3) and a refractive index difference (Δn3) less than or equal to -3.5.10-3, the width of the depressed cladding (r3-r2) being less than 5 µm. The optical fiber has an effective area larger than 120 µm2 with a cut-off wavelength limited to 1600 nm without degradation of other optical parameters of the optical fiber as compared with a SSMF, notably in terms of losses and dispersion.