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Using the Multi-Wavelength Meter
Displaying Wavelength and Power
To display average wavelength and total power
• Press the Avg WL key.
Measuring lasers between 700 nm and 1200 nm
After the Preset key is pressed, the input wavelength range is limited to measuring
lasers between 1200 nm and 1650 nm. This prevents the accidental display of spuri-
ous signals that may not exist. You can easily expand the input range to the full 700
nm to 1650 nm range, however you should learn how to identify spurious signals.
Spurious signals below 1200 nm may be displayed whenever low-power laser lines
(power levels near the Agilent 86120B's specified sensitivity) are present at the
input. 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 fun-
damental 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).
You can also avoid displaying this second harmonic line by reducing the peak
threshold below its preset value. Because the peak threshold level is used to deter-
mine which signals are to be displayed before amplitude corrections are applied, the
harmonic will be eliminated.
To use the full wavelength range
1 Press the Setup key.
2 Press the WL LIM softkey.
3 Press LIM OFF to remove the limits on wavelength range. All responses in the full
700 nm to 1650 nm range are now displayed.
Limiting the wavelength range
The wavelength range of measurement can be limited with the wavelength limit
function. Both start and stop wavelengths can be chosen. The units of wavelength
start and stop are the same as the currently selected wavelength units. If wavelength
44
Refer to "Defining Laser-Line Peaks" on page
52.
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