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.
