For Tech's Sake: Re-exploring Free Space Optics

Gary Arlen

Coming up with old ideas ? or, more specifically, going back to technology that was ahead of its time ? remains a delicate intellectual maneuver. How often can you be "on the threshold" of the right application? Or re-invent yourself?

Examples of "revisiting" technology abound in the frenetic mobile and wireless worlds, especially now when security and ubiquity add new reasons to revive ventures that weren't right for the times, even if the times were only 18 or 30 months ago.

For example, Free Space Optics (FSO) is finding new life. Terabeam Corp., the privately-held Kirkland, Wash., FSO pioneer, is working on a development contract with the Defense Advanced Research Projects Agency. Among other things, the secretive project would bring transportability ? if not full mobility ? to the previously fixed-location FSO wireless service. The U.S. Ballistic Missile Defense Organization is also exploring FSO communications for "undisclosed" applications.

Think of FSO as wireless fiber optics. Its proponents insist that the unlicensed, through-the-air technology is not just another wireless transmission format, thus avoiding spectrum regulatory control.

FSO has been around for nearly four decades, used discretely by NASA and military groups for short-haul links in remote locations. Terabeam touts that point-to-point "free space" air transmission ? through a "photophone"? was one of Alexander Graham Bell's favorite projects more than 120 years ago. Today's FSO incarnation runs through 1,550-nanometer lasers, with data rates of 1.25 gigabits per second. Advanced versions can move data at up to 2.5 gbps, and there are visions of 10 gbps versions, making FSO a wireless alternative for Gigabit Ethernet applications.

FSO's breakthrough has always been "just around the corner," although that may be stretching the analogy for this line-of-sight system. Perhaps its prospects were misty because of FSO's natural deterrents ? especially its susceptibility to fog and other weather barriers. Nonetheless, its devotees have labored on. AirFiber Inc., a privately-held San Diego FSO equipment maker, introduced a hybrid system, blending 60 gigaherz millimeter wave technology (i.e. "radio") into the system. AirFiber claims the set-up provides 99.999 percent availability through fog and rain.

As FSO found new life in the past few years, it also found new adherents. A 2000 study envisioned that the global market for FSO equipment would jump from $100 million that year to $2 billion by 2005, about half of that business in the United States. FSO has heretofore been more appealing in foreign markets, where T1 costs are prohibitive.

FSO's security strength has added to its recent appeal. The optical signal is hard to intercept because a receiver would have to be placed directly into the thin, invisible light path. The presence of such an interrupting device is immediately apparent, because it would halt legitimate connections. This assurance, plus the relative ease of installation attracted Wall Street's attention to FSO, triggering substantial installation in and near lower Manhattan after Sept. 11, 2001.

For example, Merrill Lynch and Co. quickly installed a Terabeam FSO systems to link its offices in that area after the disaster. Since then, Merrill Lynch has maintained the FSO links to back-up its traditional fiber optic connections.

Cost is also attractive. AirFiber says its FSO technology can be installed in less than three days at a cost of about $20,000 per building. That compares to fiber optic installations that take months and cost up to $200,000 for comparable service.

Terabeam's DARPA contract takes the technology in a new direction. The classified project involves development of components that would use Terabeam's technology as a mobile communications tool. Details are not available, but the venture implies entirely new markets for this broadband service.

It also demonstrates the value of persistence. As FSO companies struggled for decades to find niches in the broadband business, they sought to piggyback onto local area networks ? offering links around or between corporate or academic campus sites. FSO's signal limitations ? usually one to two miles and always line-of-sight ? turned off many prospective customers.

But like other wireless broadband hopefuls ? including today's Wi-Fi wannabes ? the FSO faithful are finding new life as broadband demand explodes, and security becomes an even more critical attribute.

Terabeam Chairman Daniel Hesse, insists that FSO's time has come because carriers and customers are looking beyond traditional T1 connectivity.

"The cost tradeoff of T1s makes wireless start to look financially attractive," Hesse, a former top AT&T Wireless executive, told Wireless Week magazine this month.

After so many faltering starts, FSO could easily fall into that black hole described as "The technology of the future, and always will be."

Its revival in an environment where wireless broadband has gained a new kind of perceived value, and where versatile, agile delivery is critical, proves that it's worth hanging on to some beliefs?even if the successful implementation is not what was originally envisioned.

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