Application: Random Polarization Scrambling - Keysight Technologies N778-C Series User Manual

4 User Interface Reference

Application: Random Polarization Scrambling

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In random scrambling mode, polarization changes are created by setting
all (virtual) waveplates to a sequence of randomized rotation angles at an
adjustable clock rate.
The scrambler operation is activated by clicking on the
Sequence/Scramble tab of the N7786C instrument. This dialog also
provides parameters settings for the scrambling operation.
Scrambling is implemented by randomly generating a special
look-up-table. The sequence length can be chosen by the field sequence
length, the repetition rate and the number of repetitions. A number of 0
repetition means an endless running sequence with the defined sequence
length.
If Synchronization is set to Auto Repeat, the scrambling sequence is
processed repeatedly without any external synchronization. The sequence
will be randomized initially and will be repeated unchanged.
If Synchronization is set to Auto Oneshot, the scrambling sequence is
processed just once (the repetition value is ignored in this mode).
If Synchronization is set to External Repeat or External Oneshot, the
behavior is similar except that the sequence is restarted when a trigger
event occurs at the Trigger Input. The exact time relative to the external
trigger signal can be adjusted using the Hold off time. This value defines
the delay between the trigger pulse in 1/32 us steps up to 0.1 ms.
The external trigger signal can also be used as timebase instead of the
internal timer. In this mode the sequence table is processed at the clock
rate applied to Trigger Input. Set Synchronization to External Oneshot to
activate this function.
Keysight N778-C Series Polarization Instruments User's Guide