EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 260)

Measurement Definitions
252 PSO-200
Measurements for Constellation Charts
Measurements for Constellation Charts
Constellation chart measurements refer to parameters based on signal
properties associated with the time-less vector analysis in I and Q space.
The constellation vector analysis is described below, where measured
samples of the symbol center are assigned a vector.
Each modulation format is also associated with an ideal symbol
constellation denoted
where M is the number of symbols in the M-ary level modulation format.
The measured samples S
meas
are normalized to minimize the deviation
from the reference constellation symbols. The figure below illustrates an
example of a measured vector S
meas
(black) and its corresponding ideal
reference vector S
ref
(green).
The analysis of the deviation of the measured samples relative to the
reference symbols is conducted by the parameters defined in this section.
S
meas
n ( )
I
meas
n ( )
Q
meas
n ( )  
 
=
S
ref
r
I
ref
r
Q
ref
r
 
 
 
= r 1 M =