MOGlabs FSW4, Руководство пользователя, Страница: 31 / 72

5.4 Examples
25
long time lag in the response, or prevent the servo controller from
ever reaching stable equilibrium. The solution is to stop integrating
when the integrator reaches the saturation limit. For MOGL abs DLC
controllers, set
V
max
= 2
.
5,
V
min
= 0.
5.4 Examples
5.4.1 Analogue output of wavelength
With
k
p
= 1 and
k
i
=
k
d
= 0, the SMA output voltage will be directly
proportional to the measured wavelength relative to the setpoint.
Figure 5.3 shows an oscilloscope trace of
V
out
for an FZW measuring
the wavelength of a rapidly scanning laser, for example to optimise
the laser mode-hop-free tuning range.
Figure 5.3:
Wavelength measurement of a scanning laser. The gain was
set to 0
.
5 V
/
GHz and the ramp amplitude shows that the laser was scanning
9 GHz. Note that the discrete steps are due to the measurement time, about
15 ms per sample, not digitisation of the DAC .