EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 187)

Setting Up the Instrument in DFB Mode
Optical Spectrum Analyzer 179
Setting Up Acquisition Parameters
Setting Up Acquisition Parameters
Before performing your test, you must set the acquisition type and
parameters.
There are three types of acquisitions in DFB mode: Single, Averaging and
Real-Time.
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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.
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.