Single-mode optical fiber with segmented depressed cladding
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Solution Overview
Problem
The challenge in manufacturing single-mode optical fibers is to reduce attenuation while maintaining low leakage losses and compliance with telecommunications standards, particularly at specific wavelengths, while also reducing manufacturing costs by increasing the capacity of optical preforms.
Innovation Solution
The solution involves a single-mode optical fiber design with a central core surrounded by an outer cladding, including an inner depressed cladding and a ring, which minimizes leakage losses and macrobending losses without increasing the diameter of the depressed cladding, allowing for a larger capacity preform and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the diameter of the depressed cladding is increased to reduce leakage losses, then leakage losses are reduced, but the preform capacity is limited and manufacturing costs increase
Solution Approach 1:
The depressed cladding is segmented into an inner depressed cladding with a first outer radius and an outer depressed cladding with a second outer radius. This segmentation allows the inner depressed cladding to provide sufficient leakage loss reduction while the outer depressed cladding can be optimized for preform capacity, resolving the contradiction between reducing leakage losses and maintaining high preform capacity.
Solution Approach 2:
Different regions of the cladding are assigned different refractive index characteristics. The inner depressed cladding has a first refractive index difference optimized for containing the fundamental mode and reducing leakage losses, while the outer depressed cladding has a second refractive index difference optimized for macrobending loss reduction. This local differentiation allows each region to perform its specific function efficiently without compromising overall preform capacity.
2Loss of energy
If the depressed cladding is enlarged to reduce macrobending losses, then macrobending losses are reduced, but the preform diameter increases and manufacturing costs increase
Solution Approach 1:
The cladding structure is divided into inner and outer depressed cladding regions, each with optimized dimensions and refractive index differences. The outer depressed cladding specifically targets macrobending loss reduction through its refractive index profile, while the overall segmented structure maintains compact dimensions that preserve preform capacity and reduce manufacturing costs.
Solution Approach 2:
The outer depressed cladding is specifically designed with a second refractive index difference optimized for reducing macrobending losses, while the inner depressed cladding focuses on fundamental mode containment. This localized optimization allows macrobending loss reduction without requiring a uniform enlargement of the entire depressed cladding structure, thereby maintaining preform capacity.
3Ease of manufacture
If the preform capacity is increased to reduce manufacturing costs, then manufacturing costs are reduced, but the ability to maintain low leakage losses is compromised
Solution Approach 1:
By segmenting the depressed cladding into inner and outer regions with different refractive index optimizations, the structure achieves low leakage losses through the inner depressed cladding's design while allowing the outer depressed cladding to be optimized for cost-effective manufacturing with larger preform capacity.
Solution Approach 2:
The invention employs different refractive index difference parameters for the inner and outer depressed cladding. The first refractive index difference is optimized for leakage loss reduction, while the second refractive index difference is optimized for macrobending loss reduction and cost-effective manufacturing. This parameter differentiation enables the structure to achieve low losses while maintaining high preform capacity for reduced manufacturing costs.
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
This design achieves leakage losses of less than 0.005 dB/km at 1550 nanometers, a cable cut-off wavelength of less than 1550 nanometers, and reduced macrobending losses, while maintaining compliance with ITU-T G.652 and G.654 recommendations, thereby enhancing the optical fiber's transmission efficiency and cost-effectiveness.
Implementation Method 1
the propagation of an optical signal in a single-mode optical fiber includes a fundamental mode, typically denoted LP01, which is guided in the core, and secondary modes, which are guided over a certain distance in the core and the optical cladding
Implementation Method 2
An optical fiber conventionally includes an optical core, which has the function of transmitting and optionally amplifying an optical signal. A conventional optical fiber also typically includes an optical cladding, which confines the optical signal in the core. For this purpose, the refractive index of the core nc is typically greater than the refractive index of the cladding ng
Data Source
AI summary
A single-mode optical fiber includes a central core surrounded by an outer optical cladding. The optical fiber includes an inner depressed cladding, a ring, and an outer depressed cladding positioned between the central core and the outer optical cladding. The central core typically has a refractive-index difference (Dn1) with the outer optical cladding of between about −0.5×10−3 and 0.5×10−3. The ring typically has an inner radius (rring1) of between about 21 microns and 35 microns and a refractive-index difference with the outer optical cladding (Dnring) of between about −0.5×10−3 and 0.5×10−3. The outer depressed cladding typically has a volume (Vout) of between about 15 μm2 and 30 μm2. The ratio of the volume of the central core over the width of the ring (Vcore/wring) is typically between about 0.12 micron and 0.2 micron.