EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 72)

Setting Up the Instrument in WDM Mode
64 FTB-5240S/5240BP
Setting Up WDM Analysis Parameters
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Peak detection level (dBm): indicates the minimum power level
from where the peak can be considered as a signal.
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RBW for OSNR (nm): indicates the resolution bandwidth for the
selected OSNR value. The resolution bandwidth of an OSA
determines its ability to deal with close optical channel spacing. It
is measured as the width of the response curve at half peak power
(i.e., 3 dB down) of the instrument to a monochromatic test signal.
The instrument’s RBW value is written below the graph on the right
(below wavelength offset).
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Wavelength offset (nm): indicates the offset value applied on the
wavelength. You can use an offset to adjust your unit. This does not
replace a calibration performed at EXFO, but it can help you
achieve the specifications if you have determined that, for
example, your modules are used beyond the normal allowed use.
Entering a value in THz is not possible. The wavelength offset
appears below the graph, on the right, next to the
arrow.
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Power offset (dB): indicates the offset value applied on the power.
You can use an offset to adjust your unit. This does not replace a
calibration performed at EXFO, but it can help you achieve the
specifications if you have determined that, for example, your
modules are used beyond the normal allowed use. The power
offset appears in the graph, on the left, above the
arrow.
To edit the power offset value in percentage, press Edit % button.
The percentage value entered in Edit percentage will be
converted to a corresponding equivalent value in dB.
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Bandwidth at (dB): Set the power level used, relative to the
channel peak power, to compute the bandwidth.