Glossary
94
GTS1063 and GTS1250 GBIC Test Systems Instruction Manual
Clock
A signal that provides a timing reference.
Clock recovery
Recovering the clock from the incoming data.
dB
Decibel: a method of expressing power or voltage ratios. The decibel scale is
logarithmic. It is often used to express the efficiency of power distribution
systems when the ratio consists of the energy put into the system divided by
the energy delivered (or in some cases, lost) by the system. One milliwatt is
usually the reference for 0 decibels. The formula for decibels is:
dB
level
= 10
@
log
(level/reference)
In the electrical domain:
dB
power
= 10
@
log(P
out
/P
ref
)
= 10
@
log(V
2
out
/R/V
ref
2/R)
= 20 log(V
out
/V
ref
)
V2
ref
/50
W
=1 mW
In optical:
dBm
power
= 10
@
log(P
o
/P
ref
)
P
ref
= 1 mW = 0 dBm
dB
level
+
10 log
ǒ
level
reference
Ǔ
dB
power
+
10log
ǒ
Pout
P
ref
Ǔ
+
10log
ǒ
V2out
R
V
2
ref
R
Ǔ
+
20log
ǒ
Vout
V
ref
Ǔ
V
2ref
50ohm
+
1mW
dBm
power
+
10log
ǒ
Po
P
ref
Ǔ
P
ref
+
1mW
+
0dBm
dBm
The symbol for power level in decibels relative to 1 mW.
Demodulation
A process whereby a modulated signal is returned to its original form.
Deterministic jitter
The difference between the maximum and minimum deviations from the
expected timing positions of data after removing the random jitter.
Differential (relating to data (electrical)signal)
A signal transmission method that requires the voltage levels in a pair of
cables/signals to convey information.
Digital Signal
A signal made up of a series of on and off pulses.
Digital Transmission System
A transmission system where information is transmitted in a series of on
and off pulses.
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