Using the Optical Spectrum Analyzer
The Bandwidth/Sweep Menus
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 video bandwidth value 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.
To change the sweep time
1Press the
2Press the Sweep Time softkey.
3Toggle between selecting sweep time automatically or manually.
4Use the knob, step keys or numeric entry pad to enter the desired value.
The sweep time is the amount of time required for the optical spectrum ana- lyzer to sweep the current measurement range. The optical spectrum analyzer automatically selects sweep times based on coupling of the following instru- ment settings:
•Wavelength span
•Resolution bandwidth
•Video bandwidth
•Sensitivity
•Trace length
•Power level
Coupling of these parameters yields optimum amplitude accuracy. When cou- pled, the optical spectrum analyzer always uses the fastest sweep possible while still maintaining the specified accuracy. Coupled, sweep times range from 50 ms to a maximum value that depends on the number of trace points used to draw the trace. This relationship is shown in the following equation:
50 ms ≤ sweep time≤ ( 1s) ( trace points)
The default number of trace points is 1001, so the maximum sweep time is normally 100 seconds. When coupling is disabled, the sweep time can be set from 56.3 ms to a maximum of 1000 seconds. If you change the number of trace points, the maximum sweep time changes as well.