Keysight Technologies N4373D, User Manual

Page: 61 / 176

Measurement Concepts
Keysight
N4373D Lightwave Component Analyzer, User’s Guide 59
Differential Measurements (applies to 4-port PNA only)
Differential measurements are made on devices when the signal
on the electrical port is the difference between two electrical
signals, each of which is referenced to ground. A differential
measurement needs two input or two output channels on the
network analzyer. The optical port of the device is a third port.

For valid differential measurements, make sure the electrical
calibration of the network analyzer includes at least three ports.
For more details on differential measurements, please consult
the network analyzers user’s guide.
For differential device measurements the LCA assumes fixed
port configuration. The physical ports 1 and 4 on the network
analyzer connect to the LCA test set. The physical ports 2 and 3
on the network analyzer connect to the differential electrical
ports of the DUT. Figure 3 shows the physical setup for EO
measurement and OE measurement, respectively.
Figure 3 Differential EO (left) and OE measurement setups

(Electrical connections shown in blue, optical connections in yellow)
For the differential measurement the logical port configuration
of the network analyzer need to be set as follows:
• Logical port 1 is assigned to the single ended, unbalanced
port and
• Logical port 2 is assigned to the balanced, differential port.
DUT out

in out
in DUT

in out