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2-16
Making Measurements
Defining Laser-Line Peaks
Peak excursion The peak excursion defines the rise and fall in amplitude that must
take place in order for a laser line to be recognized. The rise and fall
can be out of the noise, or in the case of two closely spaced signals,
out of the filter skirts of the adjacent signal. The peak excursion’s
default value is 15 dB. Any laser line that rises by 15 dB and then
falls by 15 dB passes the rule. You can set the peak excursion value
from 1 to 30 dB.
Examples of valid
and invalid signals
In the following figure, three laser lines are identified: responses 1, 3
and 4. Response 2 is not identified because it is below the peak
threshold. The portion of each signal that is within the peak excursion
limits is shown in bold lines.
Because of the peak excursion rule, responses 4 and 5 are identified
as one laser line—the minimum point between 4 and 5 does not drop
to the peak excursion limit. This response has the highest power
shown, which is peak 4.
Whenever the peak threshold limit or peak excursion value is changed,
the new limits are applied to the current displayed measurements even
if the instrument is in the Single measurement mode.
To define laser- line peaks
1 Press the Setup key.
2 Press the THRSHLD softkey.