Keysight Technologies N4373D, User Manual

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Measurement Concepts
54
Keysight
N4373D Lightwave Component Analyzer, User’s Guide
Signal Relationships in Opto-electric Devices
The LCA measurement technique is built upon concepts used in
characterizing RF and microwave devices. “S-parameter” or
scattering matrix techniques have proven to be convenient ways
to characterize device performance.
The following section will discuss how similar techniques are
used in characterizing devices in the lightwave domain. This is
intended to show the basis on which EO and OE responsivity
measurements are defined.
The figure below is a general representation of a lightwave
system, showing input and output signals in terms of terminal
voltages, input and output currents, and optical modulation
power.
S-parameters are used to describe the transmitted and reflected
signal flow within a device or network. For the model, the
following S-parameters are defined:
where:

incident on E/O device

reflected from E/O device

incident on E/O device
S
11
b
1
a
1
------
a
2
0 =
 
=
S
22
b
2
a
2
------
a
1
0 =
 
=
a
1
V

1
Z
0
-------------
=
I
1

Z
0

=
b
1
V

1refl
Z
0
----------------------
=
a
2
V

2
Z
0
-------------
=