
Measurement Definitions
Optical Modulation Analyzer 265
Measurements for Eye Diagrams
IQ Skew
The IQ skew is the time difference between I and Q tributaries of the signal
for each polarization. It is defined from the mean crossing points T
cross
of I
and Q, respectively, according to
The global skew takes both polarizations into account, according to
where X and Y indexes refer to X and Y polarization states.
IQ skew is not applicable to binary modulation formats (BPSK, OOK).
IQSkew
T
cross1 Q
T
cross1 I
–T
cross2 Q
T
cross2 I
–+
2
-----------------------------------------------------------------------------------------------------------------
=
GlobalSkew
Max T
cross1
()MinT
cross1
()–MaxT
cross2
()MinT
cross2
()–+
2
-----------------------------------------------------------------------------------------------------------------------------------------------------
=
T
cross1
T
cross1 I X
T,
cross1 Q X
T,
cross1 I Y
T,
cross1 Q Y
=
T
cross2
T
cross2 I X
T,
cross2 Q X
T,
cross2 I Y
T,
cross2 Q Y
=
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