Anritsu BERTWave Series, Руководство по эксплуатации, Страница: 69 / 466

1.5 Technical Terms
1-43
1
Outline
TDECQ (Transmitter and Dispersion Eye Closure for PAM4)
TDECQ is the measured value of the eye opening of the PAM4 signal and
is calculated by the following formula.
TDECQ =
)
R Q
1
6
OMA Outer
t

( log 10
10
(dB)
Qt: 3.414 where SER (Symbol Error Rate) = 4.8 × 10
–4
(as specified
in the IEEE 802.3cd)
R: Additional noise necessary to make SER = 4.8 × 10
–4
Figure 1.5-27 The position for TDECQ measurement
Total Error
There are two methods as follows for generating bit errors.
The following bit error count corresponding to the sum of Insertion Error
and Omission Error is referred to as the Total Error.

Signal “1” bits evaluated as “0” bits (Omission Error)
 Signal “0” bits evaluated as “1” bits (Insertion Error)
Transition Time
It is the time required to transit from 20% to 80% between Level 0 and
Level 3 in the PAM4 waveform, and is measured at the position where
Level 0 and Level 3 continue for 5 symbols or more. Rise (rise time), Fall
(fall time), and Slowest (Rise or Fall, whichever is slower) can be
measured.
Undershoot
It is the ratio of the minimum power to Level 0 in the PAM4 waveform
and is calculated by the following formula:
Undershoot = Level 0 – Pmin
Outer OMA
 100
0 1
0.45
Level 2
Level 1
Level 3
Level 0
0.55
Outer OMA
6
Average
A
Outer OMA/3
Average –
Outer OMA/3