Acquiring Waveforms
3-70
CSA7000 Series, TDS7000 Series, & TDS6000 S eries Instruments User Manual
The V(f) is the frequency at which the vertical swing is one half (0.5) the V(DC)
not 0.707. The optical bandwidth therefore corresponds to the traditional
electrical bandwidth of --6 dB. During testing of optical systems by impulse
testing, the resulting impulse waveform is converted to frequency by Fourier
transform and the bandwidth is defined as --3 dB = 10 log(vertical swing at
frequency / vertical swing at DC). During reference receiver curve calculation,
however, the definition is changed to match the industry standard definition
which assumes electrical bandwidths are --3 dB = 20×log(vertical swing at
frequency / vertical swing at DC).
The curve calculation of frequency response for the unfiltered settings uses the
definition for dB and bandwidth where --3 dB = 10 log(vertical swing at
frequency / vertical swing at DC); that is, the optical bandwidth.
The curve calculation of frequency response for reference receiver settings uses
the definition of dB and bandwidth that matches the industry standard which
assumes electrical bandwidths where --3 dB = 20 log (vertical swing at frequen-
cy / vertical swing at DC).
Bandwidth for Unfiltered
Settings
Bandwidth for Reference
Receiver settings
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