Anritsu MN4765B, Operation Manual

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O/E Module MN4765B OM PN: 10410-00742 Rev. H 3-5
Operation 3-2 E/O Measurements
The bandwidth can be measured at the 3 dB roll off point in the modulator’s
response—approximately 32 GHz in this case.
Similarly, phase and group delay measurements of the modulator can also be
made by selecting the appropriate graph type. Phase is shown as part of
Figure 3-2 but a separate phase graph type or a group delay graph type can
also be selected.
Phase measurements are generally comprised of multiple phase transitions
due to the electrical length of the DUT. A representation of phase linearity
through the device can be obtained by removing the fixed electrical length.
The Anritsu VNA's reference plane adjustment can be used to compensate for
the phase change over frequency to display the variation from linear phase.
By measuring S11, the electrical input impedance (for example, return loss of
the modulator) can also be characterized. Analysis of the S11 data over
distance, using the VNA’s time domain function, can help in locating
discontinuities and imperfections in the modulator.