EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 24)

Setting Up the Optical Modulation Analyzer
16 PSO-200
Setting Other Acquisition Parameters
Setting Other Acquisition Parameters
Use the following parameters to improve the recovered waveform:

Burst sampling parameters: you can specify the number of bursts that
will be recorded or buffered by the application, as well as the number
of data points in each burst. A larger number of points will take more
time to process but provide better results.

Input pattern mode and parameters: available modes depend on the
selected modulation scheme.

Random – if random signals (live traffic or framed PRBS) or very
long patterns (2
31
-1 PRBS) are used. The constellation chart and
eye diagrams of amplitude and phase can be measured, but not
the patterns. No filtering, averaging or CD unwrapping possible.

Repetitive (unknown pattern) – if your signal under test comprises
a repetitive pattern with known word length (for example, PRBS
with header data). The pattern can also be recovered.

User-defined symbol pattern – if you know exactly the symbol
pattern or can extract it from an acquisition (such as in Repetitive
mode or if your modulation scheme is not supported by the
PSO-200). This mode improves signal processing algorithms and
allows the calculation of a symbol error rate (SER). For details, see
Importing User-Defined Symbol Patterns on page 84.

PRBS – if your signal is generated from pseudo-random binary
sequences. Since the pattern is known, you can obtain bit error
rate (BER) information and you can use the Gearbox to fine-tune
the bit alignment of your signal stream.

User-defined bit pattern – if you know exactly the sequence of bits
in your signal. As for PRBS, you can obtain the BER and are able to
use the Gearbox.
Note: Free-Run, CW and Intensity Sampling signals do not allow patterns.