Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Intelligent Machines

Light Factory

A rare look inside the world’s biggest optical-fiber plant.

  • by Katherine Bourzac
  • October 27, 2010
  • Low-loss optical fibers created by researchers at Corning Glass Works in 1970 are what made possible the Internet as we know it. These ultrathin solid glass structures transmit data in the form of light pulses, carrying everything from phone calls to streaming video. Corning remains the world’s largest manufacturer of optical fiber. The company gave Technology Review rare access to its biggest plant, in Wilmington, North Carolina, which makes fibers for long- and short-distance transmission.
Optical fibers are drawn from large “blanks” like the ones shown here being lifted from holding ovens. The blanks have two layers, both made from silicon dioxide (glass), which will form the basis for corresponding layers in the fiber: a core that transmits light very efficiently and an outer cladding that keeps the light from leaking out. Both the core and the cladding are formed when gas jets inside a high-pressure furnace (preceding image) deposit silicon and small amounts of other elements that influence the optical properties of the glass.
Inside rows of furnaces like the ones shown here, the glass blanks are heated to begin stretching them downward.
When they descend to a certain point, they’re cut into shorter pieces. The photo on this page was taken inside one of the furnaces just after the cut, leaving behind a tip that glows in the heat. This part of the factory is an older one, where the company makes specialty products; the higher-volume processes are more automated.
This story is part of our November/December 2010 Issue
See the rest of the issue
Subscribe
The shortened glass blanks are placed in tall furnaces and heated once more to begin the fiber-drawing process. The first section of glass that comes down is teardrop-shaped (above) and can’t be drawn into fiber.
A worker quickly cuts it off and lets it fall into a bin like the one shown here; this is called “dropping the gob.” (In the most up-to-date part of the factory, this step and the rest of the process are automated inside four-story-high furnaces.) After the gob drops, the glass is pulled and stretched by machines that monitor tension on the material to ensure a fiber of consistent quality. The final product is a fiber just a few micrometers in diameter. The ratio of core to cladding remains the same as it was in the glass blank, though each layer is much thinner.
The glass fiber is threaded through tubes (above) and irradiated with ultraviolet light to harden a protective polymer coating on the surface.
The finished fiber is packaged on spools (above), tested for its mechanical and optical properties, and shipped out all over the world.

Become an MIT Technology Review Insider for in-depth analysis and unparalleled perspective.

Subscribe today
More from Intelligent Machines

Artificial intelligence and robots are transforming how we work and live.

Want more award-winning journalism? Subscribe and become an Insider.
  • Insider Plus {! insider.prices.plus !}* Best Value

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus the digital magazine, extensive archive, ad-free web experience, and discounts to partner offerings and MIT Technology Review events.

    See details+

    Print + Digital Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

    Technology Review PDF magazine archive, including articles, images, and covers dating back to 1899

    10% Discount to MIT Technology Review events and MIT Press

    Ad-free website experience

  • Insider Basic {! insider.prices.basic !}*

    {! insider.display.menuOptionsLabel !}

    Six issues of our award winning print magazine, unlimited online access plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Print Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

  • Insider Online Only {! insider.prices.online !}*

    {! insider.display.menuOptionsLabel !}

    Unlimited online access including articles and video, plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.