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Measurements Applications
Measuring Signal-to-Noise Ratios
Location of noise measurements
Automatic
interpolation
When the signal-to-noise “auto” function is selected, the Agilent 86120B first
determines the proximity of any adjacent signal. If the next closest signal is
≤
200 GHz (approximately 1.6 nm at 1550 nm) away from the signal of interest,
then the noise power is measured half way between the two channels and an
equal distance to the other side of the signal of interest. See points P
n1
and P
n2
in the following figure.
If the closest signal is more than 200 GHz from the signal of interest, or if there
is no other signals present, then the noise power is measured at 100 GHz on
either side of the signal of interest. The two measured noise power levels are
then averaged to estimate the noise power level at the signal wavelength. The
noise power measurements use linear interpolation to estimate the noise
power level at the signal of interest’s wavelength.
Automatic interpolation