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Optical Sampling Modules
11.
Push the
CLEAR DATA
button on the instrument front panel.
NOTE.
If the Vert Setup dialog box covers the Histogram statistics readout at the
right side of the display, click in the Setups title bar and drag the dialog box to the
left until you can see the Histogram statistics.
12.
After a few seconds, note the Mean and the Std Dev results displayed on the
right side of the display for the selected bandwidth or
fi
lter. The mean of the
histogram is the dark level value and the standard deviation of the histogram
is the maximum RMS vertical equivalent optical noise value. Record these
values in the Dark Level and Vertical Equivalent optical noise sections of the
test record for the optical sampling module that you are testing.
13.
Repeat steps 9 through 12 for each bandwidth and
fi
lter available for the
optical sampling module that you are testing.
NOTE.
Select
Setup > Vertical
and click the
Optical
button (if not already in
the optical settings) to access the
fi
lter and bandwidth settings for the optical
sampling module you are testing.
End of Procedure
Minimum Optical Bandwidth and Reference Receiver Frequency Response
Before performing the checks for minimum optical bandwidth and reference
receiver frequency response, you need to have an understanding of what optical
bandwidth is and how it is measured.
Traditionally, the bandwidth of a device or system is de
fi
ned as the frequency at
which the power out of the same device or system is one half as compared with a
frequency near DC. In the voltage domain, the power dissipated into a resistive
load (for example, a 50
Ω
termination of a sampler) is the V
RMS
2
/R where V
RMS
is
the RMS of the voltage swing seen at the resistive load, and R is the resistance
value. A logarithmic scale using decibels is typically used to describe a frequency
dependent response of a system.
A value expressed in terms of a decibel relative to a reference is de
fi
ned as:
For electrical bandwidths, the power ratio is used so:
when
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DSA8300 Performance Veri
fi
cation
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