Tunable Lasers How to Modulate a Signal
148 Agilent 8163A/B, 8164A/B & 8166A/B Mainframes, Sixth Edition
1 Choose a “master” source module. Set as folows:
Menu -> Modulation Source -> internal
Menu - > Modulation Frequency - > desired value
Menu - > Output trigger mode -> Modulation
2 Set all “slave” modules:
Menu -> Modulation Source -> Backplane (new for DFB
modules)
Menu -> Output trigger mode -> disabled (important)
3 To pass the master trigger to the slaves, set up the mainframe through the
“Config” button under the screen:
Config -> Trigger -> Feedback
Note that the master laser must always be turned on, if one or more slaves are
on.
How to Increase Linewidth
You can use coherence control to increase the linewidth of the optical
signal output from your Tunable Laser module.
Enabling the coherence control increases the linewidth of the optical
output signal to between 50 and 500 MHz (typically). Coherence control
greatly reduces interference effects and therefore improves the power
stability in sensitive test setups.
To enable coherence control:
1 Move to the Tunable Laser channel and press [Details].
2 Move to [Mod Src] and press ENTER.
3 Move to <Coherence Ctrl.>, Coherence Control, to increase linewidth to
approximately 500 MHz.
4 Press Enter. The text CC appears in the Tunable Laser channel.
How to Set the Output Power of a Modulated Signal
All external modulation modes require you to set the output power. To set
the output power, see “How to Set the Output Power of a Modulated
Signal” on page 142.
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