Can Wi-Fi and Lasers Bridge the Last-Mile Gap?

By Ed Sutherland

January 10, 2003

Free Space Optics, or FSO, has been called fiber optics without the cable. Coupled with 802.11 networks, it could be the solution to traversing the final mile for telcos and broadband providers.

In the 1800s Alexander Graham Bell toyed with the concept of using light to relay communications. Although the inventor discarded the idea in favor of the telephone, AT&T and other telecommunication giants are now taking a second look.

Free Space Optics, or FSO, has been called fiber optics without the cable. FSO can deliver 100 Megabits per second (Mbps) data speeds over short distances without radio's spectrum shortages or the time-consuming delays of laying more fiber optic cables. As a rival to fiber optics, which has been the preferred method to deliver broadband access to corporate giants, FSO has strong potential for delivering data in the last or "final mile."

In telecommunications, the last mile refers to that short distance between the curb and your home and office. Technologies seeking to span that gap include your telephone company, DSL provider, and the cable modem company.

Perhaps best of all, the technology can be used license free.

Probably the first time the average person heard of FSO was during the aftermath of the 9/11 terrorist attacks. Miles of fiber optic cables were ripped up connecting New York City bankers, Wall Street wizards and a good portion of the core of North America's financial activity.

Unlike fiber optics which would require months for installation and red-tape, companies needing a connection right away could set up a couple laser transmitters in days on nearby rooftops and have 100Mbps data beamed between buildings. The signal must have a clear line-of-sight to work.

AT&T Sees the Light

Despite telecommunication goliath AT&T possessing around 17,000 miles of optic fiber cable in several metropolitan areas, it is that final mile which is breathing new life into FSO and offering yet another inroad for 802.11 growth. The telco giant is just one of the telecommunications titans taking a look at FSO to help bridge the final mile, allowing them to offer local phone service to homes and offices.

AT&T is reportedly wrapping up final trials of equipment from three FSO vendors. The trials are the last stage in the communication company directly offering local broadband connections to business customers. Currently, AT&T leases cables owned by the baby bells, including Verizon, SBC, BellSouth and Qwest.

AT&T's Chief Technology Officer, Hossein Eslambolchi, envisions offering businesses a FSO link within the next 6-12 months.

AT&T is investigating the possibility of overlaying FSO with a fixed wireless system. Fixed wireless works by beaming a radio signal from one building to another.

Whether a customer would receive data by radio or light would depend on the weather. Radio waves lose power (and thereby the distance a signal can travel) when they pass through rain droplets. Fog, on the other hand, hinders beams of light.

Residential FSO?

AT&T's interest in FSO is encouraging, says Heidi Eldenburg. She is the product manager for two-year-old Omnilux, and says her company uses a combination of FSO and 802.11b to beam a broadband signal to homes and small offices.

Omnilux plans to rollout it Omni-Node rooftop device this month. The device, along with custom software, allows homes and offices in sight of each other to exchange data using light-emitting diodes (LEDs.) The gadget has a range of up to a quarter-mile with data rates reaching up to 100Mbps. Once a broadband signal reaches a home or office, it is routed to computers and entertainment appliances using either an Ethernet connection or 802.11b link.

Eldenburg says the devices will enable ISPs without easy access to phone or cable infrastructure to span that valuable last mile. Several California ISPs are taking part in the trial.

Omnilux calls its product the first optical mesh network. Theoretically, one user could broadcast his broadband connection to neighbors in line of sight of his Omni-Node. But Rick Rotondo, vice president of technical marketing at Mesh Networks, says a big issue would be the density of subscribers. A mesh network would only work if there were enough users.

As for it serving as an answer to the final mile quandary: "not in my book," remarks Rotondo.

Lindsay Schroth, an analyst with the Yankee Group research firm, believes Omnilux's residential FSO is interesting, but "it is a strange way of combining with 802.11." Schroth points out the node could transfer 100Mbps, yet 802.11b can handle just 11 Mps.

Both Schroth and Rotondo believe FSO is still better suited to short-range "campus" environments.



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