Keysight Technologies 86120B, User Manual

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54
Using the Multi-Wavelength Meter
Defining Laser-Line Peaks
Limiting the input
wavelength range The Agilent 86120B’s preset condition limits the wavelength measurement range
from 1200 nm to 1650 nm. You can expand the wavelength range to cover the entire
700 nm to 1650 nm range. Although wavelength range limiting reduces the number
of laser lines found, its main purpose is to eliminate the identification of second har-
monic distortion products as described in the following sidebar.
To define laser-line peaks
1 Press the Setup key.
Distortion caused by low-power laser lines
Low-power laser lines (power level near the Agilent 86120B’s specified sensi-
tivity) may be accompanied by second harmonic (or other) distortion. For
example, a low-power laser line at 1550 nm has a second harmonic line at 775
nm. If this second harmonic is above the peak threshold level relative to the
fundamental line, it is considered a peak. Its displayed power level may be
greater than that of the fundamental because the amplitude correction at 775
nm is much greater (by about 15 dB) than that at 1550 nm (the interferometer is
less sensitive at 775 nm).
To avoid displaying this second harmonic line, limit the input wavelength range
from 1200 nm to 1650 nm.
Or, reduce the peak threshold below its preset value. Because the peak thresh-
old level is used to determine which signals are to be displayed
before ampli-
tude corrections are applied, the harmonic will be eliminated.