Free space optics, while on MSO radar screens,
hasn’t yet found an application within their broadband networks

It's cool, for sure. The emerging technology of free space optics eschews that pesky transmission medium of actual physical cabling, opting instead for the metaphysical–using infrared laser beams to transmit large amounts of data through the air at high speeds. No wires, no maintenance . . . no problem.

But is it practical in the cable world today? Not exactly. Not yet, anyway.

In part, free space optics (FSO) isn't practical today for MSOs because of the technology's core functionality, namely fiber optic network extension and backup. While fiber is a major component of the networks that cable operators are running today, most aren't building fiber deep into the network, or extending fiber directly into commercial buildings. New access technologies are leveraging MSO HFC, and a capex crunch has meant that deep fiber solutions have been stashed deep in the recesses of the MSO mindset. FSO appears to be at its best when applied as a way to augment fiber deployments.

However, this isn't to say that FSO has no place in cable's future. It certainly might. Down the road, as cable operators migrate to premium services like very high-speed Internet access or cable telephony, they'll have an increasing need for network redundancy. Quality of service and carrier-class reliability are inherent and necessary if MSOs plan to offer business class SLAs (service level agreements) or lifeline telephony services anytime soon, and FSO is a pretty inexpensive way to either close gaps in cable distribution systems or to create redundant parallel paths in the trunk and backbone. But that seems a ways off.

For now, FSO is being applied almost entirely in the enterprise and telecom carrier sectors, where it's presently best suited. A recent Frost & Sullivan report says that 65 percent of 2001 FSO revenues came from enterprise customers, and another 34 percent came from telecom carriers. To muddle matters further, most of the early adopters of FSO systems aren't around today to sing its praises; much of the early FSO interest stemmed from come-and-gone CLECs like Allied Riser, Teligent and Winstar.

The carrier market is where FSO vendors see the most opportunity in the short term. As the telco market eventually rises from the ashes, carriers will be harder pressed to offer more over their fiber optic networks, and that should mean a rise in potential interest for new technologies that complement fiber infrastructures. So far, embattled carrier Qwest Commun-ications International is the only major domestic carrier to publicly back an FSO initiative. Last year, it inked a deal for gear from FSO provider LightPointe, a company funded primarily by Cisco Systems and Corning. Canadian FSO vendor fSONA lets on that it has trials with Sprint, SBC, BellSouth and at least 22 other carriers worldwide.

SONAbeam M Series
SONAbeam M Series gear
from fSONA.
But if FSO vendors plan to make any serious inroads into carrier networks, the technology will have to overcome some of the limitations that have characterized the first generation of FSO gear. Carriers are accustomed to near-100 percent reliability in their networks, having provided lifeline service since their inception. FSO will likely, at least in the short term, provide redundant links of fiber paths within their infrastructure. And if vendors can't sell carrier customers on the reliability of their redundancy solution, what good is it in the first place?

Since FSO uses a laser beam to transmit data between transceiver units, that laser must always have a clear path to travel. In crowded cities, having a clear line of sight can be problematic. Start with just the weather. Dense fog, like the kind that rolls into San Francisco seemingly every other day, can shut an FSO system down. Flying objects, even nondescript ones like small birds, can interrupt the transmission link in an instant. And with most FSO gear designed to send and receive via rooftop installations, any type of building movement can wreak havoc on an FSO system design. An FSO system must also account for buildings that sway, sink and shift in response to thermal changes, wind and weather. Such movement, although not typically noticeable to the naked eye, becomes increasingly apparent (and must be accounted for) when FSO vendors try to precisely line up laser beam pitchers and catchers from rooftop to rooftop.

One way that system designers are dealing with these reliability issues is through redundant design. By creating extra links through either ring or mesh topologies, FSO system operators can re-route traffic around broken links.

With each passing generation of FSO gear, vendors are finding ways to overcome some of the technology's early limitations through technical design and innovation.

The most notable new approach is adding wireless RF transmitters to the mix, so if the laser link goes down, wireless transmission can kick in and keep data flowing. Two leading FSO vendors have recently announced the addition of millimeter wave technology to their systems. AirFiber, for one, is going so far as to rename its system "HFR," for Hybrid Free space optic/Radio. The well-funded FSO player, backed by Nortel Networks and Qualcomm, combines carrier-class free space optical equipment with 60 GHz millimeter wave technology. Another vendor, Terabeam (backed by Lucent Technologies), also announced a millimeter wave strategy by acquiring millimeter wavelength radio maker Harmonix Corp. in July.

Still another new technical development is auto-tracking, a method that Canon USA, which markets FSO gear under the Canobeam brand name, touts in its systems. By widening the beam, and allowing for movement of plus or minus 2 degrees, Canobeam gear is designed to automatically adjust to outside influences. AirFiber and others offer similar auto-tracking and beam steering systems as well.

Where FSO may have the best chance to make a lasting impact is in metro area build outs, as an alternative to laying fiber optic cable. Whereas fiber can cost upwards of $300,000 to light up a building because of tunnel digging and securing rights-of-way, a short FSO link costs from $15,000 to $20,000 and can be set up in a matter of days. Unfortunately, no successful business model has been set up to build out metro areas thus far, and FSO certainly doesn't appear to be the technological savior of the cityscape network.