Tektronix OM4006D, User Manual

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Appendix E: Equivalent-Time (ET) oscilloscope operation
4. Now only the top slider will make any difference. Click Run to get a
repeating constellation and eye-diagram update. Click the + and – to make
0.1-ps adjustments to the top slider until the BPSK constellation shows as
perfectly straight lines connecting the two groups of constellation points as
shown above. (See Figure 18.)
5. Displaying the X-Q eye will show the BPSK signal going into the “wrong”
quadrature. When the delay is set properly the X-Q signal shown should
only be noise.
6. Shut down the RX X-polarization by again moving the polarization state
of the signal and disabling channels the RX X-polarization channels. Now
only the bottom slider will matter.
7. Move the last slider using the + and – buttons to get 0.1-ps changes until the
constellation looks as it did with the RX X-polarization channels. Once again
use the X-Q eye as a measure of residual error as well as constellation quality.
Note that the data is displayed in the X-I diagram because X and Y on the
OUI plots refer to transmitter polarization signals, not receiver outputs. When
only one transmitter polarization signal is present it is called “X.”
OM4000D Series Coherent Lightwave Signal Analyzer 133