160 8163A/B, 8164A/B, 8166A/B User’s Guide
5 Tunable Lasers
To enable external digital modulation using the Input Trigger Connector:
1 Move to the Tunable Laser channel and press [Details].
2Move to [Mod Src] and press Enter.
3Move 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 External Digital Modulation using Input
Trigger Connector on page 159. 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)
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 Keysight 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.
If external digital modulation using the Input Trigger Connector,
<Backplane>, is chosen as the modulation source, [Mod Src], the
81689A and 819xxA compact tunable laser modules behaves differently
from all other modules.
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