transmission rate of copper cablesWednesday, November 14, 2007
Atlanta – You may not be able to get blood out of a turnip,
but according to Penn State engineers, you can increase the
data transmission of Category-7 copper cables used to connect
computers to each other and the Internet.
NEXANS, the company that manufactures the cable, we have
examined the possibility of sending digital data at a rate of
100 gigabits per second over 100 meters of Category-7 copper
cable," says Mohsen Kavehrad, the W.L. Weiss Endowed Chair
professor of electrical engineering. "These are the current,
new generation of Ethernet cables."
These cables are
used to connect computers within a room or a building or to
create parallel computing systems. While the long distance
lines of most Internet systems are glass fiber optic cables,
which are very fast, copper cable is generally used for short
"In home networks, for example, it is
expensive to use fiber optic cabling," says Ali Enteshari,
graduate student in electrical engineering who presented the
team's methods to the IEEE High Speed Study Group today (Nov.
14) in Atlanta.
All transmission cables are limited by
the distance they can transmit data without degradation of the
signal. Before errors and interference make the signals
non-recoverable, cable systems use repeaters – which are
similar to computer modems – to capture, correct or recover
data, and resend it. The distance between repeaters depends on
the cable and the approach used by the modem to correct
"What we are offering is a less expensive
solution and one that is easier to build," says Jarir
Fadlullah, graduate student in electrical
Using information on specifications and
characteristics of the cables from NEXANS, the researchers
modeled the cable with all its attributes including modeling
crosstalk. They then designed a transmitter/receiver equipped
with an interference canceller that could transfer up to 100
gigabits using error correcting and equalizing
Ethernet cable like the Category 7 is made
up of four pairs of twisted wires shielded to reduce
crosstalk. Category 7 is heavier weight wire with better
shielding than Category 5 cable. Kavehrad's group did similar
analysis on the Category 5 cables in 2003.
"A rate of
100 gigabit over 70 meters is definitely possible, and we are
working on extending that to 100 meters, or about 328 feet,"
says Enteshari. "However, the design of a 100 gigabit modem
might not be physically realizable at this time as it is
technology limited. We are providing a roadmap to design a
high speed modem for 100 gigabits."
believe that two or three generations in the future, the
technology of chip circuitry will allow these modem designs to
be built. Currently, chip design is at about 65 nanometers,
but they expect in the next two generations to get to what is
required, says Kavehrad.
The amount of data encompassed
by 100 gigabits is amazing. The entire Encyclopedia Britannica
contains 1 gigabyte of information. A byte is equivalent to 8
bits, so 1 Gigabyte is equal to 8 gigabits. A rate of 100
gigabits per second over 100 meters is the transmission of
12.5 Encyclopedia Britannica sets per second.
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