NTT Labs Develops Smaller, Lighter Fiber Cable

  • Fiber Cable
  • NTT
TOKYO - Japan's incumbent telephone company, Nippon Telegraph and Telephone Corporation (NTT), announced that it has developed the world’s highest-density multifiber cable for outdoor optical fiber networks. NTT Labs, the company's research arm, increased cable density by using bend-insensitive fiber and a novel fiber ribbon that it calls “rollable optical fiber ribbon.” The ribbon consists of 0.25mm-diameter coated optical fibers that are intermittently bonded in a longitudinal direction.

The new cable has 30 percent smaller diameter and 60 percent lighter weight than conventional slotted-rod optical fiber cable.

NTT, which will begin using the cable later this month for fiber-to-the-home deployments, expects its lighter weight and smaller diameter to make installation faster and easier. The lighter fiber cable is, the more manageable it is. Fewer machines are needed to tow it, and fewer workers are needed to install it. In addition, cable with smaller diameter requires less space in conduits. Of course, the improvements in density had to be made without affecting the fiber's optical loss or mechanical stability.

NTT found that when it bundled conventional fibers tightly enough to achieve a small-diameter cable, micro bending forces increased the optical loss. By using bend-insensitive fibers, it could bundle the fibers more tightly without increasing optical loss.

NTT prefers to use ribbon fiber because it permits mass splicing, which is very efficient. However, ribbons are somewhat inflexible, so assembling them tightly can cause fiber strains. The new ribbon that NTT developed is composed of four single fibers arranged linearly, with neighboring fibers fixed together periodically. This structure enables the ribbon to be rolled up easily in optical fiber cable - which allows it to be bundled very tightly in the cable. It can still be mass-spliced, like conventional optical fiber ribbon.


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