Single-Mode Optical Fiber With Titania-Doped Cladding for Tight-Bend Coupling
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Solution Overview
Problem
Existing optical fibers face mechanical failure and high bending losses when coupled to silicon photonic devices due to tight bending radii, leading to fiber breakage and reduced lifetime.
Innovation Solution
The development of an optical fiber with a specific refractive index profile and a titania-doped outer cladding layer that provides improved mechanical reliability and low bending losses, allowing bending to radii as small as 3mm without mechanical failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical fiber is bent to tight radii (≤3mm) for coupling to silicon photonic devices, then coupling efficiency is improved, but mechanical failure and high bending losses occur
Solution Approach 1:
The patent applies parameter changes by modifying the refractive index profile parameters, specifically setting the core radius to 3.0 ≤ r1 ≤ 6.0 μm and the outer cladding radius to 30 μm ≤ r5 ≤ 50 μm, and controlling the relative refractive index differences (0.2% ≤ Δ1 ≤ 0.6%, -0.2% ≤ Δ3 ≤ -0.7%). These parameter optimizations enable the fiber to maintain single-mode operation while achieving low bending losses at tight radii of 2.5mm or less.
Solution Approach 2:
The patent employs composite material structure by creating a multi-layer cladding system consisting of a first outer cladding region (40) with higher refractive index and a second outer cladding region (60) with lower refractive index. This composite cladding structure, where region 40 surrounds the core and trench region, and region 60 surrounds region 40, provides mechanical strength and controls light propagation to reduce bending losses while maintaining reliability at tight bend radii.
2Ease of operation
If optical fiber is bent to tight radii (≤3mm) for coupling to silicon photonic devices, then coupling efficiency is improved, but bending losses increase
Solution Approach 1:
The patent optimizes parameter Δ3 (relative refractive index of depressed index cladding region) to be between -0.2% and -0.7%, and controls the trench volume |V3| to be ≤ 140%Δ-micron². These parameter changes create a depressed index cladding region that effectively confines light and reduces bending losses while allowing tight coupling radii for efficient coupling to silicon photonic devices.
Solution Approach 2:
The composite cladding structure with a depressed index trench region (30) surrounded by a higher index first outer cladding (40) creates an effective potential well that confines the optical mode. This composite refractive index profile reduces sensitivity to bending losses while maintaining the ability to couple efficiently at tight radii to silicon photonic devices.
3Ease of manufacture
If standard optical fiber structure is used, then manufacturing simplicity is maintained, but mechanical failure occurs at tight bend radii
Solution Approach 1:
The patent introduces a composite multi-layer cladding structure consisting of a core region (10), a depressed index trench region (30), a first outer cladding region (40) with higher refractive index, and a second outer cladding region (60) with lower refractive index. This composite structure is manufactured using standard optical fiber drawing techniques, maintaining ease of manufacture while significantly improving mechanical reliability at tight bend radii through the distributed stress management provided by the layered structure.
Solution Approach 2:
The patent applies local quality by creating a depressed index trench region (30) with specific refractive index characteristics localized around the core, and a first outer cladding region (40) with higher index localized at the intermediate radius. This localized modification of refractive index properties in specific radial zones provides enhanced mechanical reliability and bending loss performance while maintaining compatibility with standard manufacturing processes.
Data Source
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AI summary
An optical fiber comprising: (i) a core region (10) comprising an outer radius r1, and 3.0 ≤r1≤ 7.0 μm and a relative refractive index Δ1max and 0.32% ≤Δ1max≤ 0.5%; (b) a depressed index cladding region (30) surrounding the core region comprising an outer radius r3 and a relative refractive index Δ3 less than -0.2%, and trench volume V3 wherein 45%Δ-μm2<IV3I≤200%Δ-μm2; (c) a first outer cladding region (40) surrounding the depressed index cladding region (30) and comprising a relative refractive index Δ4 and an outer radius r4; and (d) a second outer cladding layer (60) comprising 5 wt%-20wt% titania, a relative refractive index Δ5, and a thickness TM, wherein 3 μm≤TM≤30 μm, and outer radius r5<65 μm; the optical fiber has a mode field diameter MFD1550 and 8 μm≤MFD1550<10.5 μm, a cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, and a bending loss at 1550 nm when using a mandrel comprising a radius of 2.5 mm of ≤1.0 dB/turn.