Depressed-Index Optical Fiber Structure for Low Bend Loss
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Solution Overview
Problem
Existing optical fibers with mode field diameter greater than or equal to 9 μm at 1310 nm face challenges in achieving both low macrobend and microbend losses, particularly at low temperatures, which are crucial for high fiber density cables in data center interconnects and congested duct applications.
Innovation Solution
The optical fibers feature a core region surrounded by multiple cladding regions, including an inner cladding, a depressed-index cladding region, and an outer cladding region, with a specific refractive index profile that reduces macrobend and microbend losses, meeting ITU-G.657.A2 specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the mode field diameter is increased to 9 μm or greater at 1310 nm for mode field matching, then compatibility with standard single mode fibers is improved, but macrobend loss increases
Solution Approach 1:
The patent applies local quality by creating a depressed-index cladding region with a specific refractive index profile (minimum relative refractive index ≤ -0.4%) localized at a specific radial position. This localized refractive index modification reduces macrobend loss while maintaining the required mode field diameter for compatibility with standard single mode fibers.
Solution Approach 2:
The patent changes the refractive index parameter of the cladding region by introducing a depressed-index region with minimum relative refractive index ≤ -0.4%. This parameter change optimizes the balance between mode field diameter and macrobend loss, enabling both G.657.A2 bend performance and ≥9 μm mode field diameter at 1310 nm.
2Productivity
If fiber density is increased for high density cable applications, then cable space utilization is improved, but microbend loss increases particularly at low temperatures
Solution Approach 1:
The patent applies local quality by creating a depressed-index cladding region with specific refractive index characteristics that provides localized protection against microbends. This localized refractive index modification (minimum relative refractive index ≤ -0.4%) reduces microbend loss while enabling high fiber density cable configurations.
Solution Approach 2:
The depressed-index cladding region acts as a beforehand cushioning mechanism that protects the core from microbend-induced stress. By pre-configuring the refractive index profile with a depressed-index region, the fiber is prepared to resist microbend losses before they occur, particularly important for low temperature performance in high density cables.
3Ease of manufacture
If the cladding structure is simplified to reduce manufacturing complexity, then ease of manufacture is improved, but bend performance deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the cladding region into distinct functional zones: an inner cladding region and a depressed-index cladding region with specific refractive index characteristics. This segmentation provides the necessary bend performance through the depressed-index region while maintaining a manageable manufacturing complexity through defined structural zones.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a depressed-index cladding region with minimum relative refractive index ≤ -0.4%. This parameter change achieves superior bend performance (macrobend loss ≤ 0.02 dB/turn) while maintaining a structured cladding design that can be manufactured using standard optical fiber fabrication processes.
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 fibers exhibit superior bend performance with macrobend losses less than 0.02 dB/turn and microbend losses optimized for high fiber density cables, ensuring reliable performance in data center interconnects and smaller diameter cables.
Implementation Method 1
The cladding region may include an inner cladding region surrounding the core region, a depressed-index cladding region surrounding the inner cladding region, and an outer cladding region surrounding the depressed-index cladding region. In some embodiments, the depressed-index cladding region may include a first region and a second region, wherein a relative refractive index of the depressed-index cladding region may decrease monotonically with increasing radius in the first region, and wherein the relative refractive index of the depressed-index cladding region may be substantially constant in the second region.
Data Source
AI summary
An optical fiber may include a core region and a cladding region surrounding the core region. The cladding region may include an inner cladding region surrounding the core region, a depressed-index cladding region surrounding the inner cladding region, and an outer cladding region surrounding the depressed-index cladding region. The inner cladding region may include a thickness greater than or equal to 1 μm. The depressed-index cladding region may include a first region and a second region, wherein a relative refractive index of the depressed-index cladding region may decrease monotonically with increasing radius in the first region, and wherein the relative refractive index of the depressed-index cladding region may be substantially constant in the second region. The optical fiber may achieve low microbend loss with large mode field diameter, while also maintaining low macrobend loss, low cable cutoff, and/or a zero dispersion wavelength between 1300 nm and 1324 nm.