HP 8163A Series, User Manual

Page: 105 / 207

105
Tunable Laser Sources
How to Set the Power
The Analog Output
If there is an output BNC connector on the front panel of your
Tunable Laser module, you can output a DC voltage level that is
proportional to the laser output power. The relationship between
this voltage level and the output power is not calibrated.
A t t e n u a t o r If your Tunable Laser module has an attenuator installed, the Analog Output
signal depends on the power mode you have chosen. The voltage level is
proportional to the optical power produced by the laser diode (not the optical
output power).
In <M
ANUAL
A
TT
.> Mode, the relationship between the power value, [P],
and the voltage level is only proportional to the output power if the
attenuation remains constant. The attenuator adds a constant offset to the
voltage level.
In <A
UTOMATIC
> Attenuation Mode, the laser output power, and therefore
the Analog Output signal, is not linearly proportional to the output power.
This is because the actual output optical power is derived by the optimum
combination of the laser output power and the attenuation.
Figure 5-5 Output Power and the Analog Output in <M
ANUAL
A
TT
.> Mode
Voltage, V
[P], mW
5 V
20 mW
2 mW
[A
TTEN
.] = 0 dB [A
TTEN
.] = 10 dB