Penn State researchers work to
develop optical communications system
San Francisco -- Light is better than radio waves
when it comes to some wireless communications, according
to Penn State engineers. Optical communications systems
could provide faster, more secure communications with
wider bandwidth and would be suitable for restricted
areas like hospitals, aircraft and factories.
(Media-Newswire.com) - San
Francisco -- Light is better than radio waves when it
comes to some wireless communications, according to Penn
State engineers. Optical communications systems could
provide faster, more secure communications with wider
bandwidth and would be suitable for restricted areas
like hospitals, aircraft and factories.
Sending
information via light waves either in physical light
guides or wirelessly is not new, but existing wireless
systems either require direct line of sight or are
diffused and have low signal strength. The researchers
chose to take a different approach using multi-element
transmitters and multi-branch optical receivers in a
quasi-diffuse configuration.
The system uses a
high-powered laser diode -- a device that converts
electricity into light -- as the optical transmitter and
an avalanche photo diode -- a device that converts light
to electricity -- as the receiver. The light bounces off
the walls and is picked up by the
receiver.
"Unless the walls are painted solid
black, there is no need to worry about transmission
within a room," said Jarir Fadlullah, graduate student
in electrical engineering who presented the paper
Tuesday ( Jan. 27 ) at SPIE Phonotics West Conference in
San Francisco, the paper will be published in the
conference proceedings.
The researchers tested
infrared light, but the system also will work with
visible light and ultraviolet light.
"The optical
system we have offers a very large bandwidth thus a very
high speed," said Fadlullah. "We can send one gigabit
per second or more over a gigahertz band."
The
researchers, including Mohshen Kavehrad, professor of
electrical engineering, think this looks like an ideal
system. Radio frequency systems do not require line of
sight transmission, but can pass through some substances
and so present a security problem. Light, in a room
without windows, will not escape the room, improving
security, but also allowing the same frequencies to be
used in adjacent rooms without interference. Multiple
sensors could allow the light signal to pass from room
to room or even from floor to floor. The system could
also be set up to convert the signal to electricity,
transfer it to another location and change it back to
light.
"The safest security is physical layer
security," said Mohshen Kavehrad. "If you first have to
break into the building before you can attack the
network it makes it very difficult."
He also said
an optical system can operate in locations where radio
frequency transmission would interfere with other
equipment, especially in hospitals, aircraft and even
some factories. Because this system is optical, it will
not interfere with the radio frequency emissions of
navigation equipment, medical devices or factory control
systems.
Optical transmissions can transfer
sensor data and unlike radio frequency communications,
also can distribute high-resolution images.
"One
application for this system would be wireless projection
of high definition television," said Kavehrad.
"Currently, two high definition broadcasts exceed the
bandwidth of any radio system, but with a 1.6 gigabit
per second gigabit system, two HD channels could be
broadcast."
While this application in conference
rooms could provide mobility for presentations,
applications in aircraft and medical facilities are
probably more important. Currently, wireless
communications are difficult in these situations because
radio frequency systems can interfere with equipment
using radio frequency control or communications. An
optical system can operate in the same space as a radio
system without interference.
"As far as I know,
these are the first set of measurements for indoor
optical wireless links that show the feasibility of the
highest bit rates with no line-of-sight," said Kavehrad.
"No radio system had comparable ability."
The
researchers will continue to test optical systems,
looking at visible and ultra violet light. They also
believe that light emitting diode room lighting could be
incorporated into the systems to provide a blanket
communications network. The researchers note that this
is a very green technology.
The National Science
Foundation supported this work.
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