EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 104)

Bit Pattern Analysis and the Gearbox
96 PSO-200
Performing Detailed Bit Pattern Analysis with the Gearbox
The second column represents the bit delay. In optical systems with
ultra-high bit rates, a difference of a few millimeters in fiber length
between modulators can lead to bit delays and misalignments. The
Gearbox can compensate for these induced delays.
To better understand, here is an example:
Input stream:
As received at modulator inputs (time sliced):
In this example, the Y0 input receives bits with a delay of one “word”. In
this case, the second column in the configuration file should be as follows:
X0= 3 0
X1= 2 0
Y0= 1 1
Y1= 0 0
Note: The first symbol identified will be in the time slice corresponding to the
greater delay value (t=1 in the above example).
1 1 0 1 0 1 0 1 1 0 1 1 1 1 0 0 1 1 1 1 0 0 0 0
t=
0
t=
1
t=
2
t=
3
t=
4
t=
5
X0
X1
Y0
Y1
1
1
0
1
0
1
1
0
1
0
1
1
1
1
0
0
1
1
1
1
0
0
0
0