EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 21)

Optical Modulation Analyzer 13
4 Setting Up the Optical
Modulation Analyzer
You should start by setting parameters on the PSO-200 so that acquisitions
are performed according to the signal you are analyzing and that the results
meet your needs.
You can also change some settings during an acquisition, or even
afterwards to see how it would have affected the results. See Reanalyzing
Acquisitions with New Settings on page 115.
Note: Changing settings during an acquisition will not stop it. However, acquired
bursts will be cleared and new bursts will be taken using the new settings.
Configuring the Input Signal
You will need to provide the following information about your input signal,
in order to obtain relevant results:

ITU channel and Offset: this is the signal frequency or wavelength. You
can select a channel from the ITU grid (25 GHz spacing), and if
needed, indicate an offset value of up to half the channel.
The signal spectrum needs to be within the receiver spectrum (see
Technical Specifications on page 131), otherwise the constellation
chart might be distorted and noisy, or even not visible at all.

Local oscillator: you can use the PSO-200’s internal pulsed laser source
or your own external laser source. For explanations on when and how
to use an external source, see Using an External Local Oscillator on
page 27).

Modulation scheme (DPSK, QPSK, etc.): select the scheme according
to the modulation of your signal under test. Dual-polarization signals
are prefixed with “DP” See Modulation Schemes on page 247.
The Free-Run, CW and Intensity Sampling modes allow bypassing
some signal processing algorithms for troubleshooting or other analysis
purposes. See Using Special Modulation Modes on page 24.