1. Set the OSA with a resolution of 0.1 or 0.2nm.
2. Connect OSA analyzer at monitoring poing where it is necsary to take the measures and get the spectrum.
3. Scan and save the values gotten from the OSA. Centran frequency (Fc) must be taken.
4. Into the spectrum showed by the OSA, place the vertical cursor A in (A = Fc - 0.2 nm) and the vertical cursor B (B = Fc - 0.2 nm). (Fc is the central frecuency of the lambda). For example, if the centra frecuency of the lambda is 1525.6 nm, cursor A
must be placen in "1525.6 nm - 0.2 nm = 1525.4 nm
, and cursor B
must be placed in "1525.6 nm + 0.2 nm = 1525.8 nm
as show in the picture below:
5. Get the integral power of the lambda (real power value) from A to B. In JDSU analyzer press the option "Total Power A<->B" and the analyzer sheds the optical power value of the lambda (S+N). (For example, in the pictuare above, the optical power showed by the analyzer is -21.45dBm and this value is the signal value level + the noise value level S + N
). Save that value.
6. Disconnect the lambda and scan again without change the cursors position. Then take the noise(N) power value by pressing the "Total Power A<->B" (For example in the next picture the power of noise N = 28.68 dBm
7. The values gotten must be convert to mW units with the next formula:
8. Once there are the values in mW (S+N and N) we must use the next formula to found the real OSNR of the signal: