High Density Fiber Optic Ribbon Cable Without Buffer Tube
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Solution Overview
Problem
Conventional optical communication cables with high fiber densities face challenges in fitting into existing ducts with small diameters due to their large outside diameters, leading to increased installation costs and difficulties in handling and splicing, especially with rollable ribbon concepts that lack solid structure.
Innovation Solution
The solution involves removing the buffer tube and using a thin layer of polymer material extruded around the ribbon stack to maintain integrity, combined with a foam layer and a single polymeric jacket to reduce the cable's outside diameter while maintaining flexibility and tensile strength, and incorporating non-round strength elements and co-extruded features for improved access and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional buffer tubes are used to protect fiber ribbons, then fiber protection is improved, but cable outside diameter increases
Solution Approach 1:
The patent removes the conventional buffer tube entirely from the cable structure. Instead, the armor layer and/or protective jacket directly engage the ribbon stack during crush or bending, providing protection without the intermediate buffer tube that increases diameter.
Solution Approach 2:
The patent uses a thin layer of polymer material (sheath) extruded about the ribbon stack to maintain stack integrity. This thin flexible layer provides necessary protection while minimizing diameter increase compared to conventional hard buffer tubes.
2Quantity of substance
If more fibers are packed into the same space, then fiber density is improved, but cable handling and splicing difficulty increases
Solution Approach 1:
The patent inverts the conventional approach by making the ribbon stack itself rigid and structured, rather than making it flexible and rollable. This solid structure with defined ribbon orientations enables easier handling and splicing while achieving high fiber density through optimized stack configuration.
Solution Approach 2:
The patent uses a composite structure combining rigid ribbon stacks with a thin polymer sheath and foam layer. This composite approach maintains the solid structure needed for easy handling while enabling high fiber density through efficient space utilization.
3Reliability
If buffer tube wall thickness is increased, then fiber protection is improved, but cable outside diameter increases
Solution Approach 1:
The patent eliminates the buffer tube entirely, removing the source of diameter increase from wall thickness. Protection is provided directly by the armor layer and/or protective jacket engaging the ribbon stack, and by the thin polymer sheath maintaining stack integrity.
Data Source
AI summary
A fiber optic cable includes a stranded ribbon stack, a sheath extruded around the stranded ribbon stack to form a subunit, and an extruded foam layer, wherein the foam layer has a minimum inner diameter that is less than or equal to a maximum stack diagonal dimension of the stranded ribbon stack.