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O/E Measurements (Photodiodes)
O/O Measurements
Measurement Calibration
Agilent N4373A Lightwave Component Analyzer, First Edition
The measurement process for O/E devices is similar to E/O
devices. The measurement consists of the ratio of output
electrical modulation current to input optical modulation
power. Slope responsivity for O/E devices describes how a
change in optical power produces a change in electrical
current. Graphically this is shown in the figure below.
I
out
mA
The LCA measures the input optical modulation power and
output modulation current and displays the ratio of the two
in Amps/Watt.
Characteristics of purely optical devices can also be
measured. In this case, both the stimulus and response are
modulated light. The ratio measurement is simply one of gain
or loss versus modulation frequency.
The key to making accurate E/O, O/O, or O/E measurements
is calibrated instrumentation. The instrument lightwave
source and receiver are individually characterized.
The systematic responses of the components making up the
LCA can then be removed, yielding the response of the
device under test (DUT). (See "Signal Relationships in Opto-
electric Devices" on page 34 for more detail.)
Measurement Concepts
P
mW
in
(
⁄
)
Responsivity R
A W
=
r
(
R
A W
r
(
)
--------------------------- -
R
dB
=
20log
⁄
r
10
A W
∆I
out
--------------
∆
P
in
⁄
)
33
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