Tunable Lasers How to Modulate a Signal
138 Agilent 8163A/B, 8164A/B, and 8166A/B User’s Guide, Fourth Edition
NOTE If external digital modulation, <backplane>, is chosen for the DFB or
Fabry-Perot Laser modules, the applied triggering should have a 50%
duty cycle and a frequency of 200 Hz - 100 kHz.
• the average power of the output signal of the Agilent 81689A
Tunable Laser module varies in proportion with the change in duty
cycle, while,
• the power of the output signal of all other modules adjusts so that
the average power of the output signal is always 50% of the set
power.
To enable external digital modulation using the Input Trigger
Connector:
1 Move to the Tunable Laser channel and press [Details].
2 Move to [Mod Src] and press Enter.
3 Move to <Backplane>, by using the cursor key, and press Enter. The
text Back appears in the Tunable Laser channel.
External Digital Modulation Using Trigger Feedback
The trigger for External Digital Modulation can be provided by another
module in the same mainframe by using the Trigger Feedback
configuration as described on page 67. This can be used to synchronize
the modulation of several sources. To use synchronized modulation:
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.
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