Patent ID: 8787753
Filing Date: 2014-07-22
Classification: H04B

Abstract:
1. A method for determining a noise parameter on an input optical signal having a data-carrying signal contribution and a noise contribution within an optical signal bandwidth, the method comprising: obtaining at least two optical spectrum traces from said input optical signal, said optical spectrum traces being taken under different conditions such that they exhibit different non-zero signal-to-noise ratios; mathematically discriminating said signal contribution from said noise contribution within said optical signal bandwidth using said optical spectrum traces; determining an in-band noise level on said input optical signal from the discriminated noise contribution; determining the noise parameter from the determined in-band noise level, the noise parameter being indicative of the noise contribution within the optical signal bandwidth; wherein the signal contribution and the noise contribution have mutually different degrees of polarization and wherein said obtaining at least two optical spectrum traces under different conditions comprises: producing at least two samples of the input optical signal, under respective different polarization analysis conditions, said polarization analysis conditions corresponding to the at least two samples being arbitrary relative to said data-carrying signal contribution such that the data-carrying signal contribution is not substantially suppressed on any of said at least two samples, said at least two samples exhibiting mutually different non-zero signal-to-noise ratios; and acquiring an optical spectrum of each one of the at least two samples to obtain said optical spectrum traces; wherein said discriminating comprises: calculating, from said optical spectrum traces, a difference optical spectrum substantially indicative of said data-carrying signal contribution; and solving for said noises contribution using said optical spectrum traces and said difference optical spectrum.