THORLABS PICO D User Manual page 26

Table 2-7
To achieve
Shortest wavelength corresponds to –10V
Longest wavelength corresponds to +10V
Figure 2–13
Note that the this is a differential input stage and that both
+WAVELENGTH_TUNING and -WAVELENGTH_TUNING must be connected.
In order to achieve 1 pm wavelength resolution the voltage applied to the
+WAVELENGTH_TUNING terminal must be of high quality and noise free. The fol-
lowing example illustrates this critical issue.
Assume that 110 nm tuning range (i.e. 110 000 pm) is achieved by a 20 V control
voltage (peak-to-peak). This means that the voltage step is 20 V/110 000 pm ≈ 180
µV/pm. Alternatively, a D/A converter resolution better than
bits. Hence a D/A converter with minimum 18 bit capacity is recommended.
2.5.4.2 Analog control: OPTICAL_POWER
Provided that _OPTICAL_POWER_ENABLE is set TRUE – LOW, the optical power
can be set and changed by applying voltage to +OPTICAL_POWER and -OPTI-
CAL_POWER as shown in Table 2-8 and Figure 2–13.
Table 2-8
To achieve
Optical power off corresponds to –1 V
Lowest optical power corresponds to 0 V
Maximum optical power corresponds to +10 V
26
Setting the WAVELENGTH_TUNING voltage
Schematic picture illustrating the relation between the wave-
length tuning signal and the emitted laser wavelength.
corresponds to the shortest and the longest wavelengths, respec-
tively (see the technical specifications for numerical values).
Setting the OPTICAL_POWER voltage
Settings
-WAVELENGTH_TUNING set to 0 V and
+WAVELENGTH_TUNING set to -10V
-WAVELENGTH_TUNING set to 0 V and
+WAVELENGTH_TUNING set to +10V
2
log(110 000) > 16.7
Settings
-OPTICAL_POWER set to 0V and
+OPTICAL_POWER set to -1V
-OPTICAL_POWER set to 0V and
+OPTICAL_POWER set to 0V
-OPTICAL_POWER set to 0V and
+OPTICAL_POWER set to +10V
λ λ
and
1 2