Optical Fiber Trench Cladding for Low Macrobend Loss
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Solution Overview
Problem
Optical fibers used in submarine systems experience unreasonably high macrobend losses due to mechanical stress, which is not adequately addressed by existing designs optimized for terrestrial applications.
Innovation Solution
The optical fibers feature a relative refractive index profile with a trench cladding region that minimizes macrobend loss at large bend diameters, specifically designed to reduce trench volume, resulting in reduced macrobend loss at bend diameters greater than 40 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard submarine fiber designs are used, then the fiber can be deployed in submarine environments, but macrobend loss becomes unreasonably high due to mechanical stress from large bend diameters
Solution Approach 1:
The patent applies local quality by creating a trench cladding region with distinct refractive index properties (lower than both core and outer cladding) at a specific radial position. This localized modification of the cladding structure directly addresses the macrobend loss problem at large bend diameters without altering the overall fiber design, providing targeted improvement where needed while maintaining standard submarine fiber deployment capabilities
Solution Approach 2:
The patent changes the refractive index parameter distribution by introducing a trench region with lower refractive index than the outer cladding. This parameter modification (creating a refractive index well at radial position r3) fundamentally alters the optical confinement characteristics, enabling the fiber to maintain low macrobend loss at large bend diameters (greater than 40 mm) while remaining adaptable to submarine deployment environments
2Loss of energy
If trench volume is reduced in the cladding region, then macrobend loss decreases at large bend diameters, but the complexity of manufacturing precise refractive index profiles increases
Solution Approach 1:
The patent specifies precise parameter ranges for the trench region (radial position r3, refractive index Δ3, and volume constraints) to achieve low macrobend loss. By defining clear parameter boundaries and relationships (such as the trench volume being less than 35% μm² and specific refractive index differences), the patent balances manufacturing feasibility with performance requirements, making precise refractive index profiling achievable through controlled parameter selection
Solution Approach 2:
The patent focuses manufacturing precision efforts on the specific trench region rather than the entire fiber structure. By localizing the complex refractive index modification to a defined radial position and volume, the manufacturing complexity is concentrated and manageable, allowing standard submarine fiber production processes to be used with added precision only where the trench is formed
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 achieves macrobend loss of less than 0.001 dB/turn at 1550 nm when tested with a 50 mm mandrel, significantly improving performance at large bend diameters compared to conventional submarine fibers.
Implementation Method 1
The optical fiber has a relative refractive index profile designed to minimize macrobend loss at bending diameters typically encountered in submarine systems. The relative refractive index profile includes a cladding with a trench configured to minimize macrobend loss at bend diameters greater than 40 mm.
Implementation Method 2
As the optical fiber bends, a fraction of the optical signal refracts out of the core and is dissipated in the protective coating surrounding the fiber.
Data Source
AI summary
The present disclosure provides optical fibers that exhibit low macrobend loss at 1550 nm at bend diameters greater than 40 mm. The relative refractive index profile of the fibers includes a trench cladding region having a trench volume configured to minimize macrobend loss at large bend diameters. The thickness and/or depth of the trench cladding region are controlled to reduce trench volume to a degree consistent with reducing macrobend loss at bend diameters greater than 40 mm. The optical fiber includes an outer cladding region that surrounds and is directly adjacent to the trench cladding region and an optional offset cladding region between the trench cladding region and the core region. In some embodiments, the core region is a segmented core region that includes inner and outer core regions. The low macrobend loss available from the optical fibers makes them particularly suitable for applications in submarine telecommunications systems.