Tektronix OM4006D, User Manual, Page: 106 / 205

Core processing software guide
Signal processing steps in CoreProcessing
CoreProcessing.m is a long fi le because it includes all the signal processing options
for the many possible modulation formats. There are several “switch SigType”
statements, where one case includes some repetition of code from an earlier case.
If a user is interested in only one modulation format it is expedient to delete all
the case statements that are not of interest (after making a copy of the original
CoreProcessing.m). The resulting
fi le will be shorter and easier to navigate.
A fi le CoreProcessing1chQPSK .m, located in the same folder as
CoreProcessing.m, has been prepared in this way to process single polarization
QPSK signals. It can be called by replacing the line in the MATLAB Commands
Window “CoreProcessing” with “CoreProcessing1chQPSK”. The processing
stages in CoreProcessing1chQPSK will be studied now, as an example of how
the full CoreProcessing works. The headings of the sections that follow are
the same as the headings (comment lines) within CoreProcessing1chQPSK.
The following diagram shows how the processing is applied to signals at three
different sample rates.
The appearance of the single channel QPSK signal is shown below, as the
processing progresses. The signal has X and Y polarization components, each
of which is shown as a plot on the complex plane.
82 OM4000D Series Coherent Lightwave Signal Analyzer