THE ALL-FIBER NETWORK

The need to convert photons to electrons and back again in order to manage them has been one of the most annoying problems to pester the telecom industry in the past few decades. The effort and expense required by optical-electrical-optical, or OEO, conversions have incited multiple quixotic remedies, from all-optical hardware that preserves photons (e.g., Corvis) to integrated photonics vendors that cut the cost of OEO conversions (e.g., Infinera) to research into silicon lasers (e.g., Intel). The ultimate in all-optical networks may be all-fiber networks, in which the functions performed today by big hunks of hardware (switching, monitoring, etc.) are in the future performed beneath the glass of the fiber itself.

Researchers from Pennsylvania State University, Cambridge and the University of Southampton took a significant step toward the achievement of that dream recently by demonstrating the construction of a gas-based semiconductor inside an optical fiber.

The researchers — whose work was published in the March issue of Science — used microstructured, or “holey,” fiber, so called because of the tiny holes inside the glass where light signals don't go. They filled the holes with germanium, a semiconductor gas, to see if they could build a semiconductor device inside those holes that could interact with the optical signal beaming alongside it.

“What's surprising is how perfectly the process works,” said John Badding, associate professor of chemistry at Penn State and one of the authors of the paper.

Researchers stopped just short of filling the hole entirely with germanium. But their control over the process was so precise that they were able to leave a gap of only 25 nanometers in diameter. That's roughly a million times thinner than a human hair.

The achievement suggests that these in-fiber semiconductors could be used to generate, modulate and detect photonic signals. “The fabrication of [in-fiber semiconductor devices] would be a major step toward all-fiber optoelectronics,” the researchers wrote.

“That means the signal never leaves the fiber,” Badding said. “This is exciting because we can perhaps think about putting some of the functions now done outside the fiber into [it].”

However, the step taken by his team is an early one. He doesn't expect it to touch the telecom industry for at least another five to 10 years. Still, Southampton researchers have a reputation for real-world impact. They were the ones who developed erbium-doped fiber amplifiers, which use erbium to amplify signals in fiber without having to convert them into electrons in back — a development that revolutionized telecom economics. Perhaps the method pioneered by Badding's team will one day give birth to an even greater revolution in all-fiber networks.