Multimode Optical Fiber with Buried Trench for Low Bending Losses
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Solution Overview
Problem
Multimode optical fibers face challenges in achieving high bandwidth and reduced bending losses, especially at wavelengths of 850 nanometers and 1300 nanometers, while minimizing the cladding effect, to support high-data-rate applications over long distances.
Innovation Solution
The optical fiber design incorporates a central core with an alpha-index profile, an inner cladding, and a buried trench, where the refractive index differences and widths of these components are optimized to satisfy specific inequalities, resulting in reduced bending losses and enhanced bandwidth, with a buried trench volume and outer radius that facilitate low bending losses and high bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the core diameter is reduced from 62.5 microns to 50 microns to increase bandwidth for high-data-rate applications, then the bandwidth is improved, but the bending losses increase
Solution Approach 1:
The patent applies local quality by creating a buried trench with a specific refractive index (lower than both core and outer cladding) at a specific location between the core and outer cladding. This localized modification of the refractive index profile reduces bending losses in the 50-micron core while preserving the high bandwidth characteristics, without requiring a change to the overall core diameter.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a buried trench with a refractive index lower than both the core and outer cladding. This parameter modification (creating a depressed region) allows the fiber to maintain low bending losses while keeping the 50-micron core diameter optimized for high bandwidth applications.
2Loss of energy
If a buried trench is introduced to reduce bending losses, then the bending losses are reduced, but the device complexity increases
Solution Approach 1:
The patent segments the cladding region into two distinct parts: an inner cladding adjacent to the core and an outer cladding surrounding the inner cladding, with the buried trench positioned between them. This segmentation allows independent optimization of each region's refractive index to achieve low bending losses while maintaining manufacturability through standard deposition processes.
3Reliability
If the refractive index difference is increased to reduce the cladding effect, then the cladding effect is reduced, but the bending losses increase
Solution Approach 1:
The buried trench acts as an intermediary layer with a refractive index lower than both the core and outer cladding. This intermediate region mediates the optical field distribution, reducing the cladding effect on higher-order modes while simultaneously reducing bending losses by confining the optical field more effectively during fiber bending.
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 solution achieves bending losses of less than 0.2 dB for two turns around a 7.5 mm radius at both 850 nanometers and 1300 nanometers, with an overfilled launch bandwidth of at least 500 MHz·km at 1300 nanometers and an outer DMD value of less than 0.33 ps/m, meeting OM3 and OM4 standards, and supports data rates of 10 Gb/s over 100 to 300 meters.
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.
Data Source
AI summary
A multimode optical fiber includes a central core, an inner cladding, a buried trench, and an outer cladding (e.g., an outer optical cladding). Typically, the optical fiber's central core is a glass-based central core having an alpha-index profile (i.e., a graded-index profile), an outer radius r1, and a maximum refractive index difference Δn1 with respect to the outer cladding. The central core's alpha-index profile has a minimum refractive index at the central core's outer radius r1 that corresponds to a refractive index difference Δnend with respect to the outer cladding. The inner cladding has an outer radius r2, a width w2, and a refractive index difference Δn2 with respect to the outer cladding. The buried trench has an outer radius rext, a width w3, and a refractive index difference Δn3 with respect to the outer cladding. The multimode optical fiber typically has reduced bending losses, a high bandwidth at wavelengths of both 850 nanometers and 1300 nanometers, and a reduced cladding effect.