Inverse Triangular Trench Fiber for Bend Loss and Connectivity
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Solution Overview
Problem
Traditional single mode optical fibers with small mode field diameters achieve low bending loss but suffer from connectivity issues when connected to standard fibers, leading to increased connectivity losses.
Innovation Solution
Optical fibers with an inverse triangular trench design and a mode field diameter of 9 microns or greater, featuring a depressed-index cladding region with increasing relative refractive index, providing bend insensitivity across various diameters while maintaining connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single mode optical fibers use small mode field diameters (8.5-8.8 microns) to achieve low bending loss and G.657 compliance, then bend insensitivity is improved, but connectivity losses increase when connected to standard single mode optical fibers with nominal mode field diameter of 9.2 microns
Solution Approach 1:
The patent changes the mode field diameter parameter from the traditional small value (8.5-8.8 microns) to a larger value (9.0 microns or greater), while simultaneously modifying the refractive index profile parameters (depressed-index cladding region with increasing relative refractive index Δ3) to maintain G.657 bend performance compliance. This parameter transformation resolves the contradiction by achieving both improved connectivity and maintained bend insensitivity.
2Loss of energy
If the mode field diameter is increased to 9.0 microns or greater to improve connectivity with standard fibers, then connectivity losses are reduced, but bend insensitivity deteriorates and G.657 compliance is lost
Solution Approach 1:
The patent applies local quality by creating a depressed-index cladding region with specific spatial characteristics (increasing relative refractive index Δ3 with radial position) that locally modifies the optical field distribution. This localized refractive index modification enables the fiber to maintain small effective mode field confinement (for bend insensitivity) while allowing a larger overall mode field diameter (for connectivity), thus resolving the contradiction between these two opposing requirements.
Solution Approach 2:
The patent employs a composite refractive index structure combining a core region with maximum relative refractive index Δ1max and a surrounding depressed-index cladding region with increasing relative refractive index Δ3. This composite index profile creates distinct optical zones that work together to simultaneously achieve large mode field diameter (for connectivity) and small effective confinement (for bend insensitivity), resolving the technical contradiction.
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 low bend losses and improved connectivity by ensuring compliance with G.657 standards across all bend diameters, reducing losses to less than 0.75 dB/turn at 15 mm, less than 0.2 dB/turn at 20 mm, and less than 0.005 dB/turn at 30 mm.
Implementation Method 1
A cladding region surrounds the core region, the cladding region comprising a depressed-index cladding region, a relative refractive index Δ3 of the depressed-index cladding region increasing with increased radial position
Data Source
AI summary
A single mode optical fiber is provided that includes a core region having an outer radius r1 and a maximum relative refractive index Δ1max. The single mode optical fiber further includes a cladding region surrounding the core region, the cladding region includes a depressed-index cladding region, a relative refractive index Δ3 of the depressed-index cladding region increasing with increased radial position. The single mode optical fiber has a bend loss at 1550 nm for a 15 mm diameter mandrel of less than about 0.75 dB/turn, a bend loss at 1550 nm for a 20 mm diameter mandrel of less than about 0.2 dB/turn, and a bend loss at 1550 nm for a 30 mm diameter mandrel of less than 0.005 dB/turn. Additionally, the single mode optical fiber has a mode field diameter of 9.0 microns or greater at 1310 nm wavelength.