Patent ID: 8358930
Filing Date: 2013-01-22
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 show different non-zero signal-to-noise ratios, mathematically discriminating said signal contribution from said noise contribution within said optical signal bandwidth based on a mathematical combination of said optical spectrum traces, determining an in-band noise level on said input optical signal from the discriminated noise contribution, and 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 at least one of different degrees of polarization and different states of polarization from one another and wherein said obtaining at least two optical spectrum traces comprises: wherein said polarizing at least part of the input optical signal comprises polarization beam splitting said input optical signal into said samples, said samples having states of polarization orthogonal from one another; wherein said discriminating comprises: wherein said optical spectrum traces each have a signal contribution and a noise contribution and wherein said performing calculations further comprises estimating a factor K related to a proportion between the signal contributions of said optical spectrum traces for use in said estimating an optical spectrum of said input optical signal; wherein said calculating further comprises: