MEMORY LANE: Got a Light?

Sat, 10/31/2009 - 8:20pm
Stewart Schley, Media & Technology Writer

Cable’s adoption of fiber optics got its start in Georgia,
but the breakthrough occurred at a lab in England

For the cable industry, the city of Augusta, Ga., enjoys special prominence, because it was there that one of the first wide-scale commercial deployments of optical fiber took place. In 1989, engineers at Jones Intercable, a Denver-based cable company, had become convinced that they could improve the quality and reliability of video signals by displacing Stewart Schleylengthy runs of amplified cables with fiber-optic lines. It wasn’t the coaxial cable itself they had identified as a problem, but the cascades of electronic amplifiers that reenergized signals along the way, each time introducing a small amount of noise that worsened the signal’s quality as the line extended on.

But fiber optics would change that. Powered by laser transmitters made by a predecessor of Antec Corp., the fiber lines in Augusta beamed signals cleanly and clearly to RF interface points, proving to Jones Intercable and the cable industry that fiber optics represented a leap forward in signal distribution.

For the next 10 years, the cable industry would deploy fiber optics at a feverish rate, until nearly all of the industry’s systems had adopted a blend of fiber and coaxial networking known as hybrid fiber/coax, or HFC, that prevails today.

Cable’s adoption of fiber optics may have gotten its start in Georgia. But the breakthrough that enabled Jones Intercable to even contemplate the idea occurred more than 20 years earlier at a laboratory in Harlow, England.

It was there – at a facility operated by the Nortel predecessor Standard Telephones and Cable – that a Ph.D. candidate at the University of London worked as an engineer and researcher. Charles Kao, born in 1933 in Shanghai, had been working for several years to try to understand a frustrating limitation of existing fiber-optic networks. Although highly promising in their ability to transmit large amounts of information over sliver-thin glass strands, optical fibers were lousy with signal loss. Attenuation, or the gradual loss of signal intensity, ran as high as 1,000 dB per kilometer, meaning barely 1/100th of the transmitted optical power would reach the receiver – and making fiber impractical as an alternative to radio waves or microwave.

Kao’s important realization was that the problem with optical signal degradation wasn’t the fault of the optics, but of the transmission vessel. Impurities in glass strands used to convey light sapped the beam’s intensity, Kao believed. If engineers could find the right physical material, it could be possible to dramatically extend the distance over which optical fiber could faithfully transmit information.

With a team of researchers, Kao began exploring the use of fused silica, a purer transmission medium. When Kao proved that optical signals could travel close to 60 miles when sent through a nearly pristine fiber, it sparked a wave of investment in fiber optics development and manufacturing. In the 1970s, a team of engineers at Corning developed a glass pure enough to exhibit attenuation of less than 20 dB per km, a key performance indicator that would make fiber optics suitable for commercial deployment.

In the ’70s, the U.S. military began to deploy fiber-optic networks, and telephone companies AT&T and GTE followed. The first commercial deployment of fiber optics for television came in 1980, as ABC-TV employed a fiber-optic network to shuttle backup signals of its coverage of the Winter Olympics from Lake Placid, N.Y. As the cable industry sought to improve signal transmission later in the 1980s, fiber became the medium of choice, with Jones Intercable’s deployment in Augusta closely watched throughout the industry.

It’s interesting now to realize how Kao’s work and theories in the 1960s conflicted with prevailing beliefs. Many engineering experts in the telecommunications world were convinced fiber optics would never emerge as a legitimate competitor to prevailing transmission mediums and looked on Kao’s work with great skepticism. That certainly has changed: The contributions of fiber optics, and of Kao, were recognized in October when the Shanghai-born engineer was awarded the Nobel Prize for Physics.

Kao himself, though, seems to regard his work with little sense of ego. In a 2008 oral history interview conducted by the IEEE, Kao said: “I still feel that it is not the invention of something that is important. It is how we can utilize that then to improve life that is important.”

To say life has been well-served by fiber-optic networks seems like an understatement. Within seconds, it’s now possible to transmit information across the globe over a lattice of optical networks, from just about anywhere in the developed world. Including Augusta.



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