Setting Up Osnr Analysis - EXFO OSA20 User Manual

Setting Up OSNR Analysis

The OSNR analysis tool is available in OSA, SML, WDM, RLT and OFA analysis modes.
Defining OSNR Analysis Parameters
The OSNR tool allows you to get the calculated Optical Signal to Noise Ratio of a laser peak
(in dB).
OSNR Calculation
IEC standard 61280-2-9
For data rates < 10 Gbits/s and for non-modulated signals, the calculation of the OSNR
follows the equation defined in the IEC standard 61280-2-9:
Where:
Pi is the optical power of the channel in Watts.

Ni is the interpolated noise power in Watts measured in the resolution bandwidth of the

OSA20.
RBW

RBW

N

corr
In case of OSA20, a correction factor is added to account for the Gaussian shape of the
filtering, instead of the rectangular shape obtained at larger bandwidth.
The standard also indicates that the calculation of Ni, usually not measurable due to the
presence of the signal peak, needs to be done based on interpolation (i.e. a fit) of the noise
spectrum close to the signal. You must note that the measured signal is in fact the sum of
P +N .
i i
OSA20
is the resolution bandwidth of the OSA20.
OSA
is the reference optical bandwidth, chosen to be 0.1 nm.
ref
is the noise correction:
Analyzing Traces
Setting Up OSNR Analysis
97