Cabletron Systems 100BASE-FX, Cabling Manual

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Test Characteristics 2-7
Cabling Terms
Delay
The term delay, when applied to network cabling, typically refers to the
propagation delay of the segment or network. As signals in both electrically
conductive cables and fiber optic cables travel through the transmission media at
a fraction of the speed of light, there is an appreciable delay between the
transmission of a signal on one end of a cable and the reception of the same signal
on the other end. Network delay is typically measured in microseconds (
µ
s). One
microsecond is equal to 1/1,000,000 of a second.
Attenuation
Attenuation is the reduction of signal strength in a cable as a result of absorption
or dispersion of the electrical or optical impulse traveling through the cable. The
effect of attenuation is a gradual decrease in the power or clarity of a signal after it
traverses a length of cabling. The measure of the attenuation of a cable is
expressed in decibels (dB).
There are two different measures of attenuation that are important from a
networking point of view. The first is the attenuation characteristics of a cable.
These are estimates of the expected attenuation that a signal will suffer for
passing through a given length of the cable. Expected attenuation values are
expressed in dB/m, dB/km, or dB/ft.
The second measure of attenuation is that which is determined by testing a length
of cable to determine its total attenuation. Total attenuation takes into account all
components of the cable run and is expressed as a total measure of signal loss in
decibels from one end of the cable to the other.