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Function Reference
OSNR Marker
Center amplitude
OSNR =
--------------------------------------------------- -
(
)
N
normalized
a
Interpolating Noise
To accurately measure noise, the noise level must be determined at the signal
wavelength. The measurement cannot be directly performed because the sig-
nal power level masks the noise. To estimate the noise at the signal wave-
length, the OSA measures the noise power above and below the channel
wavelength at the predetermined offset or pits (depending on the Noise
Method selected in the Marker Setup panel). Next, the values are linearly
interpolated to determine the noise value at the channel wavelength.
Error Messages
OSNR error messages are displayed in red letters and are described below
with suggestions to correct the error.
Noise Not Found can be displayed for two different conditions. The first
condition occurs when Pit mode is selected, and the left or right marker is
unable to find a pit using the Pit Excursion (selected in the Marker Setup
panel).
The second condition occurs when auto or manual mode is selected and the
left or right marker is outside the span. In this case, the noise measurement is
made at the span's end point.
3-52
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