EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 107)

Setting Up the Instrument in WDM Mode
Optical Spectrum Analyzer 99
Setting Up Acquisition Parameters
Setting Up Acquisition Parameters
Before performing your test, you must set the acquisition type and
parameters.
There are four types of acquisitions in WDM mode: Single, Averaging,
Real-Time and In-Band.
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Single: Spectral measurement is performed once. The results are
displayed according to this measurement. In single mode, noise
measurement can be performed In-Band if the option is available.
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Averaging: Spectral measurements are performed based on the
number of scans that you have entered for this parameter. The trace
will be displayed after each acquisition and averaged with the previous
traces.
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Real-Time: In Real-Time acquisition, spectral measurements are
performed continuously until you press Stop. No averaging is done for
spectral measurements. The graph and results are refreshed after each
acquisition.
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In-Band: The In-Band method can be used to measure noise in some
or all channels. This mode will perform a series of scans in different
polarization conditions in order to accurately calculate the In-Band
OSNR measurements for each signal.
Note: The In-Band option is available only if the module supports it.
Before performing measurements on an optical spectrum, you must select
the wavelength/frequency range to use. You can perform the scan on the
full range, on spectral bands, or select a custom range.
Note: The shorter the wavelength or frequency range, the faster the acquisition.