Opening up a new world by achieving ultra-high fiber count optical fibers

To achieve high fiber counts, the number of fibers used must be increased. Optical fibers are glass fibers as thin as a human hair and coated with a thin layer of resin. In general, the outside diameter is about 0.25 mm, and the necessary number of fibers is stranded as discussed earlier. The strand is jacketed with robust plastic materials to manufacture optical cables. Obviously, the capacity can be increased by accommodating more fibers in a cable at high density. Previously, the average fiber count of optical cables was about 100. In Japan, which is an advanced country in using high-fiber-count cables, the maximum fiber count that is generally used is about 1000. Sumitomo Electric made efforts to reduce the outside diameter of cables with the same fiber count, and accumulated technologies to achieve high density. However, new customers for optical cables emerged, and their needs were completely different from the conventional ones. It all started in the winter of 2014. Nobuyuki Suzuki, who is currently the president of Sumitomo Electric Lightwave Corp. (SEL) that serves as the strategic company in the optical communication business in the U.S. market, was affiliated with the Optical Fiber & Cable Div. in Japan and was engaged in a project to increase the fiber count and develop technologies for new cables. Suzuki was informed by SEL that a customer needed a high-fiber-count cable that was friendlier to use at data centers. At that time, the maximum fiber count of cables used in the U.S. was 864.

When the development process of the 3456-fiber-count optical cable is discussed, it is necessary to understand the ribbon fiber and pliable ribbon. A ribbon fiber refers to fiber array in which multiple optical fibers are arranged in parallel and coated together. It is characterized by excellent implementation efficiency compared to a conventional single fiber. The time required for the splicing work can be reduced significantly because mass fusion splicing can be performed for each ribbon fiber. A newly developed 12-fiber pliable ribbon that had partial slits between fibers (slotting a 12-fiber-count ribbon which was the mainstream outside Japan) was employed. Suzuki’s partner in this development project was Tsuguo Amano, who is currently Engineering General Manager of the Optical Fiber & Cable Dept.

“The technical issue was how to accommodate optical fibers at high density in the limited space while maintaining the transmission characteristics. A pliable ribbon attains both flexibility and ribbon alignment during mass-fusion splicing. This pliable ribbon was employed in combination with optical fibers with bending loss insensitive property and an excellent non-preferential bending slotted core cable structure design with a central tension member (which relieves the tension that is applied to optical fibers during installation). As a result, the fiber density in the cable core was improved dramatically. These designs were developed patiently through trial and error, but the development process was speedy. As a result, the fiber counts doubled compared to the conventional products of the same outside diameter. Amazingly, this was equivalent to 1728 fiber counts for 1.5-inch cable ducts and 3456 fiber counts for 2.0-inch cable ducts, achieving world-class ultra-high fiber counts.

In line with these development efforts, the manufacturing capabilities of the production sites that were refined through many years of operation were demonstrated at an extraordinary speed. The world’s first 3456-fiber-count was delivered at the beginning of 2016.

Conventionally, the optical cable business of the Sumitomo Electric Group focused on the Japanese market. For this reason, the business inevitably became sluggish as the market matured. It was innovative for the optical cable business to develop the ultra-high fiber count cable and open up new markets outside Japan. Suemori clearly remembers the customer saying “crazy” when he presented the 3456-fiber-count optical cable. The word showed surprise at the quick development of the high-density cable, and was the ultimate compliment.

SEL (led by President Suzuki) approached the customer who operated hyperscale DCs in the U.S. Senior Vice President Barrett Mills (sales supervisor) points out that the business cycle of hyperscale DC operators is very fast.

“At present, we can offer cutting-edge products by developing products through close cooperation between SEL and Sumitomo Electric. However, we are not sure about the customers’ needs and market situation in two years. The advancement of customers’ businesses has been accelerating. Under these circumstances, we must maintain a certain level of presence based on ultra-high fiber count optical cables. To this end, we must offer comprehensive solutions, including both ultra-high fiber count optical cables and peripheral equipment for optical fibers, for customers’ networks. Meanwhile, we will strengthen our relationships with construction contractors to further enhance our support system for customers.”

Sumitomo Electric pioneered the field of ultra-high fiber count optical cables, but the competition has been intensifying as competitors have caught up. To maintain a certain level of presence and continue to support the cloud society, the Sumitomo Electric Group has been taking on new challenges with the next generation in mind.