Characterization of non-ASE noise on optical signals

A method for determining a noise parameter characterizing an optical signal-under-test having a signal contribution, an Amplified Spontaneous Emission (ASE) noise contribution and a non-ASE optical noise contribution within an optical-signal bandwidth, wherein said signal contribution is polarized and wherein said non-ASE optical noise contribution comprises a depolarized-signal contribution, said method comprising:

• acquiring, for each of a number nSOP of varied state-of-polarization analysis conditions of the signal-under-test, at least one polarization-analyzed optical spectrum trace using an optical spectrum analyzer;
• using a spectrum processor, discriminating at least said non-ASE optical noise contribution from said ASE-noise contribution using at least one of the at least one polarization-analyzed optical spectrum trace and a trace obtained from the at least one polarization-analyzed optical spectrum trace;
• using a noise calculator, determining said noise parameter characterizing said signal-under-test using at least one of the discriminated non-ASE optical noise contribution and the discriminated ASE-noise contribution;
• and
• outputting said noise parameter;
• further comprising:
• determining an extrema trace from the at least one polarization-analyzed optical spectrum trace;
• wherein said discriminating is made using said extrema trace.