HP 70000 series - Lightwave Signal Analyzer Operation

Refer to the Figure A-3 for an overview of the modules that are available for an
HP 70000 Series modular spectrum analyzer system.
Lightwave Signal Analyzer
The HP 70000 Series modular lightwave signal analyzer system combines a photoreceiver
module, an HP 70810B lightwave section, with an HP 70000 Series modular spectrum analyzer
system. A standard HP 71400C lightwave signal analyzer is a combination of an HP 70810B
lightwave section and an HP 71210C microwave spectrum analyzer. A standard HP 71401C
lightwave signal analyzer is a combination of an HP 70810B lightwave section and an
HP 71100C modular spectrum analyzer. Other modules are added to the standard lightwave
signal analyzers to enhance the capabilities of the system. Refer to the Figure A-3 for an
overview of the modules that are available for an HP 70000 Series modular lightwave signal
analyzer system.
A lightwave signal analyzer displays the total average power and modulation, or base band
spectrum, of an optical input signal. Figure A-2 illustrates a basic lightwave signal analyzer.
Modulated light enters the HP 70810B lightwave section through a singlemode-ber front panel
connector. The light is expanded, collimated, and passed through an optical attenuator that is
controllable over a 30 dB range in 1 dB steps. The attenuator can be used to prevent front-end
overload.
The collimated light is then focused onto a PIN photodetector. Electron-hole pairs are
generated
by
the
light
in
the
photodetector
,
producing
a
photocurrent.
The
dc
photocurrent
is
measured
by
an
average
power
meter
and
amplied
by
a
100
kHz
to
22
GHz preamplier.
The
preamplier
amplies
the
signal
by
32
dB
to
improve
the
sensitivity
of
the
analyzer. The
amplied
signal
passes
to
the
input
of
the
HP
70000
Series
modular
spectrum
analyzer
system
that has been mated with the lightwave section. The detected modulation, or base-band
spectrum,
is
then
processed
and
displayed.
A-2 Theory of Operation