Flexible High-Fiber-Count Cable With Fire-Retardant Jacket
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Solution Overview
Problem
Conventional high-fiber-count cables are stiff and difficult to bend, making them challenging to route and install in confined spaces within data centers, and they do not meet the fire safety requirements for both indoor and outdoor use across different global regions.
Innovation Solution
A flexible optical fiber cable design with a thick fire-retardant outer jacket and subunits containing optical fibers, using fire-retardant polymers and strengthening yarns, and incorporating a water barrier layer, which meets UL 1666 and EN 50399 burn test requirements, and allows for flexible routing and installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional high-fiber-count cables are used to achieve high fiber density, then fiber count is improved, but cable flexibility deteriorates making them stiff and difficult to bend
Solution Approach 1:
The cable is divided into multiple independent subunits, each containing a specific number of fibers (e.g., 72 fibers per subunit). These subunits are arranged in layers and can move independently relative to each other, allowing the cable to bend flexibly while maintaining high total fiber count. The segmentation enables the cable to achieve both high fiber density and flexibility.
Solution Approach 2:
The patent changes the physical parameters of the cable structure by using a flexible outer jacket material and optimizing the arrangement of subunits in layers. The outer jacket is designed with specific mechanical properties to allow bending without damaging fibers, while the layered arrangement of subunits enables the cable to achieve desired flexibility while maintaining high fiber count.
2Reliability
If PVC materials are used to meet UL 1666 fire safety requirements, then fire safety is improved, but compatibility with EN 50399 CPR requirements deteriorates due to halogenated compounds
Solution Approach 1:
The patent changes the chemical composition parameters of the outer jacket material by formulating a polymer composition that is halogen-free (removing PVC and halogenated compounds) while maintaining fire safety through alternative flame retardant mechanisms. This allows the cable to meet both UL 1666 and EN 50399 CPR requirements simultaneously.
Solution Approach 2:
The outer jacket is made from a composite polymer material that combines multiple components to achieve both fire safety and halogen-free requirements. The composite formulation includes flame retardant additives and polymer matrices that work together to provide fire resistance without relying on halogenated compounds, enabling compliance with both American and European fire safety standards.
3Reliability
If cable jacket thickness is increased to improve fire safety performance, then fire resistance is improved, but cable flexibility deteriorates
Solution Approach 1:
The patent optimizes the thickness parameter of the outer jacket to a specific range (0.5-2.0 inches or 12-50mm) that balances fire safety performance with flexibility. The jacket is designed with sufficient thickness to meet fire safety requirements while maintaining mechanical flexibility for routing and installation. The optimal thickness prevents excessive rigidity while providing adequate fire protection.
Solution Approach 2:
The outer jacket is designed with differentiated local properties - the material composition and thickness are optimized specifically for the regions where fire safety is critical, while maintaining overall flexibility. The jacket structure allows for localized fire resistance where needed while preserving global flexibility for cable routing and installation.
Data Source
AI summary
An optical fiber cable that includes subunits is provided. The cable has an outer jacket having a thickness of at least 2.0 millimeters and that is made from a fire retardant polymer material having a PHRR value of 222 kw/m2 when tested in a cone calorimeter measured according to ASTM E1354 with a heat flux of 50 kW/m2. The cable meets the requirement of UL 1666 burn test for riser cables and the requirements of EN 50399 burn test for CPR class Cca cables.