Patent ID: 8666244

Claim:
A method of monitoring optical parameters of a modulated optical signal, the method comprising: receiving a first optical power, X i , of said optical signal for a first bandwidth, B i , across said optical signal; receiving a second optical power, X j , of said optical signal for a second bandwidth, B j , across said optical signal; obtaining a power spectral density description of said optical signal, wherein said power spectral density description comprises, a first k number, k i , dependent on a total noiseless optical power of said optical signal and an optical power determined from a power spectral density of said optical signal across said first bandwidth, B i , and a second k number, k j , dependent on said total noiseless optical power and an optical power determined from said power spectral density across said second bandwidth, B j ; receiving a reference bandwidth, B 0 ; measuring said first optical power, X i , of said optical signal across said first bandwidth, B i ; measuring said second optical power, X j , of said optical signal across said second bandwidth, B j ; and determining an optical signal to noise ratio, osnr, of said optical signal, said optical signal to noise ratio depending on said first optical power, X i , said second optical power, X j , and said power spectral density description, wherein said osnr is determined as o ⁢ ⁢ s ⁢ ⁢ n ⁢ ⁢ r = B j B 0 ⁢ X i - B i B 0 ⁢ X j X j k i - X i k j ; and generating a data signal indicative of said optical signal to noise ratio.