Non-Zero Dispersion Shifted Fiber With Buried Trench
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Solution Overview
Problem
Existing non-zero dispersion shifted fibers (NZDSFs) face challenges in achieving low bending losses and large effective areas while maintaining compatibility with other optical fibers, particularly at large radii of curvature, and existing solutions either result in high attenuation or are difficult to manufacture.
Innovation Solution
A non-zero dispersion shifted optical fiber design featuring a central core, an inner cladding, and an outer cladding with a specific refractive index profile, including a buried trench and multiple intermediate claddings, which optimizes refractive index differences and radii to achieve low bending losses and high effective areas without increasing non-linear effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional NZDSF designs are used, then chromatic dispersion is reduced, but bending losses increase at large radii of curvature
Solution Approach 1:
The optical fiber is divided into multiple functional zones: a central core for signal transmission, an intermediate cladding with first refractive index, a buried trench with second refractive index, and an outer cladding with third refractive index. This segmentation allows each zone to contribute differently to the overall optical properties, enabling simultaneous optimization of chromatic dispersion and bending loss characteristics.
Solution Approach 2:
Different regions of the optical fiber are assigned different refractive index characteristics: the central core has higher refractive index for confinement, the intermediate cladding provides transition, the buried trench creates a local refractive index minimum to reduce bending losses, and the outer cladding provides final confinement. This local differentiation enables the fiber to achieve both low chromatic dispersion and low bending losses.
2Power
If effective area is increased to reduce non-linear effects, then transmission power can be increased, but fiber structure complexity increases
Solution Approach 1:
The optical fiber employs a nested cladding structure where the intermediate cladding surrounds the central core, the buried trench is embedded within the intermediate cladding, and the outer cladding surrounds the entire inner structure. This nested arrangement achieves complex optical properties through hierarchical organization of simpler components, managing structural complexity while enabling large effective area for high-power transmission.
3Loss of energy
If refractive index differences are optimized for low bending losses, then chromatic dispersion characteristics deteriorate
Solution Approach 1:
The invention optimizes specific parameter ranges: the ratio of the buried trench outer radius to central core outer radius is maintained between 0.8 and 1.2, the refractive index differences are constrained within specific ranges (first difference greater than second difference, both positive), and the outer cladding refractive index is kept lower than both inner cladding refractive indices. These parameter optimizations enable simultaneous achievement of low bending losses and acceptable chromatic dispersion.
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 proposed fiber design achieves bending losses of less than 0.5 dB/100 turns at 30mm radius of curvature and an effective area of at least 95 µm² at 1550nm, while maintaining compatibility with other optical fibers and reducing attenuation, thus enabling higher transmission powers without increasing non-linear effects.
Implementation Method 1
An optical fiber (i.e., a glass fiber typically surrounded by one or more coating layers) conventionally includes an optical fiber core, which transmits and/or amplifies an optical signal, and an optical cladding, which confines the optical signal within the core. Accordingly, the refractive index of the core n c is typically greater than the refractive index of the optical cladding n g (i.e., n c > n g ).
Data Source
Figure 1~2
AI summary
A non-zero dispersion shifted optical fiber (NZDSF) includes a central core, an inner cladding, and an outer cladding. The central core has an outer radius r1 and a maximum refractive index difference Dn1 with respect to the outer cladding. The inner cladding includes a first intermediate cladding and a buried trench. The first intermediate cladding has an outer radius r2 and a refractive index difference Dn2 with respect to the outer cladding. The buried trench has an outer radius r3, a width W3, and a negative refractive index difference Dn3 with respect to the outer cladding. In some embodiments, the inner cladding includes a second intermediate cladding having an outer radius r4 and a refractive index difference Dn4 with respect to the outer cladding. For a radius of curvature of 30 millimeters at a wavelength of 1625 nanometers, the optical fiber typically exhibits bending losses of about 0.5 dB/100 turns or less. At a wavelength of 1550 nanometers, the optical fiber's effective area is typically about 95 µm2 or greater.