e.
RNG:
This option appears only if “DGD Only” is selected for option b). It allows the
user to set the lower and upper DGD limits for the scan.
Range:
0.0 to 91.0 for 90 ps PMDPro.
0.4 to 182.4 for 180 ps PMDPro.
4.
PMD TRACE SCAN:
Continuous mode PMD scan: Unlike the discrete mode scan, which generates a
series of discontinuous PMD states according to the lookup table, the continuous
mode scan varies the PMD continuously, with a user-controllable variation rate.
This function is therefore ideal for PMD tracking speed tests.
The DGD/SOPMD combinations available in quasi-continuous mode are points
on one of the characteristic SOPMD vs. DGD curves.
90ps PMDPro
0
500
1000
1500
2000
2500
0
20
40
60
80
100
DGD (ps)
SO
PM
D (
p
s
2
)
Figure 7 Characteristic SOPMD vs. DGD curves
In the PMD Trace scan function, the PMDPro traces out a demi-arc of a
characteristic curve. Each demi-arc is half of a characteristic curve, with one
endpoint on the DGD axis, as illustrated in Figure 7. The user selects a particular
demi-arc to be traced by specifying a DGD value. The PMDPro then matches the
specified value to the demi-arc with the DGD axis endpoint closest to that value.
The PMDPro can also step through a series of points along a demi-arc with a
constant, user-controllable DGD step size. This is the step trace function. The
transient between consecutive points in a step trace follows the characteristic
curve, so that there are no discontinuous jumps during travel along a particular
arc.
Document #: GP-UM-PMD-1000-21
Page 21 of 122
