4-82
Remote Operation
SENSe Subsystem Commands
[SENSe:]BANDwidth|BWIDth:VIDeo <numeric_value> [HZ|KHZ|MHZ|GHZ]
[SENSe:]BANDwidth|BWIDth:VIDeo?
Specifies the bandwidth of the post-detection video filter. The minimum value
for the video bandwidth is 0.1 Hz. The maximum value is the lesser between
3 kHz and the bandwidth of the currently selected transimpedance amplifier.
Available choices move in a 1, 3, 10 sequence.
[SENSe:]BANDwidth|BWIDth:VIDeo:AUTO OFF|ON|0|1
[SENSe:]BANDwidth|BWIDth:VIDeo:AUTO?
The
[SENSe:]BANDwidth|BWIDth:VIDeo:AUTO
command enables and disables
automatic coupling of the video bandwidth.
Video bandwidth filtering occurs after detection of the light. In the autocou-
pled mode, the video bandwidth has an extremely wide range. This allows the
optical spectrum analyzer to avoid unnecessary filtering that would reduce the
sweep speed more than required.
Normally, the video bandwidth is coupled to the sensitivity. Manually entering
a video bandwidth breaks this coupling. The video bandwidth can be manually
set from 100 MHz to 3 kHz, or the bandwidth of the currently selected tran-
simpedance amplifier, whichever is less.
The following functions affect video bandwidth:
• Changing the sensitivity value.
• Changing the reference level.
• Turning autoranging
ON
or
OFF
.
The range of video bandwidth available in
Auto
mode is much greater than can
be set manually from the front panel. A lower value of video bandwidth
requires a longer sweep time. Because of the interdependence between the
video bandwidth and sensitivity, it is recommended that either the sensitivity
or
the video bandwidth be changed, whichever is the most important to the
measurement task being performed.
Because of the interdependence of sensitivity and video bandwidth, these
parameters cannot be set individually. If one of the parameters is set manually,
the other is forced into Auto coupled mode and set by the instrument. Set
either the desired sensitivity or the desired video bandwidth, depending on
which parameter is most important to the current measurement task.
The Preset state of the video bandwidth coupling is AUTO.
book.book Page 82 Monday, January 31, 2000 10:34 AM
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