Extreme Density Calls for Extreme Cables
While bandwidth across the globe continues to grow at a drastic rate, the need for fiber optic cables with extremely high fiber counts, known as Extreme-High-Density Cables, has become even more essential. AFL defines Extreme-High-Density Cabling as any fiber-optic cable with 1,728 fibers or more. Due to the large fiber count, these cables have become very popular among large data centers, whose business model is fitting high fiber counts in small footprints. In the November/December 2020 issue of Cabling Installation and Maintenance, Patrick Dobbins, the Director of Solutions Engineering for AFL, provided us with information on these cables including its biggest users, its technology, recommendations on installation and more.
As the cost of rights-of-way are very high in urban underground networks, many of these competitive access networks are attempting to maximize the use of underground conduit systems. Current users of extreme high-density cable include Hyperscale data centers that utilize mesh architecture for computing. This requires a high number of connections and parallel processing of information that drives up the number of fibers and interconnection to storage devices. Other users of extreme high-density fiber optic cables are distributive access networks, dense urban access networks that interface with wireless low power WAN systems, and competitive Access Providers.
AFL’s SpiderWeb Ribbon® (SWR®) technology has allowed us to achieve these high fiber counts within a small-diameter cable. Developed by our parent company, Fujikura of Japan, SWR is available in both 250 µm and 200 µm fiber. This ribbon technology allows for the ribbon to fully collapse and creates a high packing factor of ribbon into a cable that has been optimized to reduce the diameter. The individual 12-fiber ribbons have fibers that are intermittently bonded to the adjacent fiber like a spider web. This allows for the fiber to align into a flat ribbon that can be mass fusion spliced, but still collapsed to permit a dense packing factor. Each of these ribbons are individually marked with band marking for identification down to an individual fiber color.
The collapsible ribbon is arranged by binder grouping of 12 ribbon or 24 ribbon groupings known as binder groups, which follow the industry-standard color code for identification. All the binders are grouped in the core of the cable with water-blocking yarns to provide resistance to moisture migration down the core of the cable. This core of ribbon binder groups and water-blocking yarns are covered with a water-blocking tape and an outer sheath with strength members embedded in the jacket. It has two ripcords and a rib indicator on the jacket to identify the location of the ripcords to facilitate mid-cable access. This cable is known as Wrapping Tube Cable (WTC) with SpiderWeb Ribbon (SWR), and it typically is a 35% reduction in diameter and 50% reduction in cable weight from traditional ribbon cables.
In the 200 µm version of AFL’s SpiderWeb Ribbon, the fibers have a cladding of 125 µm + 0.7 µm and core that is approximately 8.6 µm + 0.4 µm. This is a dual-listed fiber that is compliant with ITU-T G.652.D and G.657.A1. What makes this unique is that the ribbon “pitch,” or the spacing between the fibers in the ribbon, are based on 250 µm. When the coating is removed on the fibers of the SWR ribbon, the center of the cores is spaced the same as a 250 µm traditional flat matrix ribbon for mass fusion splicing. Additionally, the 200 µm SWR can be de-ribbonized and spliced using single fusion. In this case, a core alignment splicing machine could be used to splice to traditional 250 µm single fibers. The evolution of mass fusion splicing equipment and mass fusion splice fiber holders and accessories such as the thermal strippers and cleavers, play a major role in making this kind of technology possible. These strippers and cleavers are both optimized to improve efficiency and splicing time of extreme high-density cables.
Although there is not special installation treatment required for extreme high-density fiber optic cables, good construction techniques and prudent care when handling these cables will yield good results. Normal care and good practices are important as the dollar value of these extreme high-density cables is much higher. One of the best ways to manage extreme high-density fiber cable is to organize the fiber in a splice closure tray or optical entrance enclosure tray in order to keep the binder identification all the way to the splice tray. The color coding of the fiber in the ribbon identifies the fiber number, the band marking keeps the ribbon number identification, and binder color code keeps the binder number identified. This makes identifying a specific circuit easy to locate in the splice tray without having to trace back to the organizer basket or cable core.