Rethinking optical fiber

Rethinking optical fiber and its contribution to a $7.5 trillion industry

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A shocking opening sentence introduces the featured article of the September Journal of the American Ceramic Society. “From a materials perspective optical fibers are victims of their own success,” write John Ballato and Peter Dragic in the abstract.

The abstract continues, “The advent of the laser, 50 yr ago, coupled with an insatiable demand for information enabled by light-based communications, ushered in a golden age of glass science and engineering. It is somewhat ironic that the staggering ubiquity of information today, which is carried globally and almost instantaneously via optical fibers, is enabled largely by one material—silica—into which only a few components are added. The richness of the Periodic Table has largely been forgotten.”

The paper, titled “Rethinking optical fiber: New demands, old glasses,” is a not-so-subtle challenge to the glass and optics community—including industrial manufacturers—to break the inertia that dominates current optic materials technology.

The optics industry has a lot of inertia. Not because it is stagnant, but because it is so large. In a 28-minute video abstract, Ballato, a professor of materials science at Clemson University, says, “The annual application of light annually, globally, is about a $7.5 trillion business. The use of light globally as a market is about half the GDP of the entire United States. So it is a humongous market. That global market enables pretty much everything you think about when you think about communications today.”

An online article in the Washington Post provides some additional context. Only about five percent of all households in the US still rely on copper wire systems, so-called “plain old telephone service,” or POTS. According to the article, telecommunications companies spend about $16 billion annually to maintain these networks. Right now, regulation is forcing their upkeep, but eventually they are likely to be replaced by fiber optic networks or a combination of cellular and fiber optic.

“Optical fibers enable a considerable fraction of that global optics business,” Ballato says in the video, and just about every signal will pass through an optical fiber at some point on its path around the world.

Today, optical fiber systems are straining to meet signal demand that were impossible to foresee 40-plus years ago. Materials need to be rethought to meet the exploding demands from users for increased cell phone use, texting, internet media streaming, national defense and security networks, and other closed networks. Also, higher-bandwidth fibers are needed to transmit laser light via fiber optic for manufacturing—laser cutting, laser welding—and surgical tools.

But Ballato also says bluntly, “Optical materials from a materials perspective are remarkably boring.” Commercial optical fibers are made of silica with few percent of dopants to craft the optical properties.

What he means is that other well-known families of glasses and photonic crystals could meet our burgeoning communication needs if we are willing to remove “the imposition that fibers have to be made as they have been for 40 yr.” In the paper, he concedes, “practicality and industrial relevance do set useful limitations on the selection of ‘novel optical glasses.’” That is, new materials for optical systems must be compatible with existing silica-based infrastructure, especially regarding strength, splicing, mode, and attenuation.

Ballato and Dragic, a professor at the University of Illinois at Urbana-Champaign, review the merits of several alternative systems for making optical fibers, including YAG-derived, sapphire-derived, spinel-derived, and BaO-derived optical fibers. (The image above shows several. See caption below for details.) Not surprisingly, new materials need new processes. Instead of the old CVD and draw tower processes, these new materials are made by a “molten-core” fabrication process. The approach has the advantage of enabling ordinary materials that are not generally suitable for optical fiber cores for processing reasons, to be fiberized. (See the May issue (pdf) of the ACerS Bulletin for a detailed description of the process.)

Ballato and Dragic’s paper is unusual for a scholarly article. It is technically rigorous, but they set out to provoke—which they do successfully—and they make good use of humor. That is all I’m going to say—read the paper yourself or watch the video!

The time seems to be ripe for the next big thing in optics and glass. In a report in the Oct/Nov ACerS Bulletin, Carlo Pantano reported on the January conference on emerging technology challenges for developing functional glasses for new energy and information applications. Coming up in May 2014, the ACerS Glass and Optical Materials Division will hold its annual meeting in Aachen, Germany, in cooperation with the Deutsche Glastechnische Gesselschaft, which will include the 10th International Conference on Advances in Fusion and Processing of Glass. Organizers are actively soliciting papers now. With a piece of a $7.5 trillion market in play, you may want to be there.

The paper is “Rethinking optical fibers: New demands, old glasses,” by John Ballato and Peter Dragic. (DOI: 10.1111/jace.12516)

Featured image caption: Optical micrograph of spinel‐derived (i) and BaO‐derived (ii) fiber cross sections, splices between silica and the (iii) spinel‐derived and (iv) BaO‐derived fibers. In (iii) and (iv), “SpDF” refers to the spinel‐derived optical fiber and “BaODF” refers to the BaO‐derived optical fiber. (Credit: Ballato and Dragic; Wiley.)

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