Hollow Core Optical Fiber Structure for Higher-Order Mode Suppression
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Solution Overview
Problem
Hollow core photonic crystal fibers suffer from high-order mode contamination and are not purely single mode waveguides, making it difficult to launch a pure LP01 mode without higher-order mode (HOM) contamination, and they are sensitive to bending and have high loss.
Innovation Solution
A hollow core photonic crystal fiber design with seven non-touching hollow tubes, each with a specific diameter ratio and spacing, optimized for low loss and high suppression of higher-order modes, achieving a low loss transmission band with a bandwidth of at least 50 nm and insensitivity to bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If hollow core photonic crystal fiber is used to achieve low propagation loss and high damage threshold, then transmission loss is reduced and damage threshold is improved, but higher-order mode contamination occurs and single mode operation becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the diameter ratio (d/D ≈ 0.68) and wall thickness ratio (t/D = 0.01) of the hollow tubes to achieve resonant filtering. This specific parameter configuration creates resonant phase-matched coupling that selectively suppresses higher-order modes while maintaining low loss for the fundamental mode, resolving the contradiction between low propagation loss and single mode operation.
Solution Approach 2:
The patent implements local quality by designing hollow tubes with specific localized properties (diameter ratio d/D ≈ 0.68 and wall thickness ratio t/D = 0.01) that are optimized for resonant filtering. These locally optimized structures are positioned at specific locations in the cladding to create resonant coupling zones that selectively affect higher-order modes without impacting the fundamental mode transmission.
2Adaptability or versatility
If hollow core photonic crystal fiber is used to achieve broad spectral transmission, then spectral bandwidth is improved, but higher-order mode contamination increases
Solution Approach 1:
The patent uses parameter changes by optimizing the hollow tube dimensions (diameter ratio d/D ≈ 0.68 and wall thickness ratio t/D = 0.01) to create a resonant filtering mechanism that operates across broad wavelength bands. This resonant coupling effect maintains high suppression of higher-order modes throughout the broad spectral range, enabling both broad spectral transmission and high mode purity.
3Ease of manufacture
If conventional hollow core fiber design is used to simplify structure, then manufacturing complexity is reduced, but higher-order mode suppression is insufficient
Solution Approach 1:
The patent applies parameter changes by specifying precise dimensional ratios (diameter ratio d/D ≈ 0.68 and wall thickness ratio t/D = 0.01) that enable resonant filtering. This approach maintains relative structural simplicity while achieving high HOM suppression through carefully controlled geometric parameters rather than complex multi-layer 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 design achieves high suppression of HOMs, low loss in the fundamental mode, and insensitivity to bending, with a broad transmission band and high beam quality, supporting wavelengths from 400 nm to 1200 nm with losses below 50 dB/km.
Implementation Method 1
The kagome type fiber guides light by means of an anti-resonant effect
Implementation Method 2
hollow-core photonic bandgap fibers
Data Source
AI summary
A hollow core photonic crystal fiber (PCF) including an outer cladding region and seven hollow tubes surrounded by the outer cladding region. Each of the hollow tubes is fused to the outer cladding to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region. The hollow tubes are not touching each other but are arranged with distance to adjacent hollow tubes. The hollow tubes each have an average outer diameter d2 and an average inner diameter d1, wherein d1/d2 is equal to or larger than about 0.8, such as equal to or larger than about 0.85, such as equal to or larger than about 0.9. Also, a laser system.