Keysight Technologies N4374B, Руководство пользователя

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Measurement Concepts
Keysight
N4374B Lightwave Component Analyzer, User’s Guide 47
It is interesting to note that delta voltages and currents are used
as opposed to RMS values. This is done because we deal with
modulation signals in describing lightwave transducers, where a
change in optical power is proportional to a change in electrical
current or voltage.
The overall system forward gain is defined as:
Though the overall system gain is defined as an S-parameter, the
individual transfer functions of the EO and OE devices are
typically defined in terms of responsivities, because signals in
both the optical and electrical domain are used and optical
signals do not lend themselves conveniently to S-parameter
definitions. Initially, the input impedance of the EO converter
and the output impedance of the OE converter will be assumed
to be Z
0
(thus S
11
and S
22
are zero).
and
Using the above relationships, we can rewrite S
21
in terms of the
transducer responsivities R
s
and R
r
:
reflected from E/O device
(no reverse transmission is
assumed)
b
2
V
Δ
2refl
Z
0
---------------------
I
2
Δ
Z
0
•
S
21
b
2
a
1
------ a
2
0
( )
S
12
0
R
s
P
0
Δ
I
i
Δ
-----------
E/O source responsivity
R
r
I
2
Δ
P
0
Δ
-----------
O/E receiver responsivity
S
21
b
2
a
1
------
I
2
Δ
I
1
Δ
---------