Patent ID: 7116454
Filing Date: 2006-10-03
Classification: H04B

Abstract:
1. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal, the method comprising the steps of: calculating characteristic histogram moments from the measured amplitude histogram; measuring directly an optical signal-to noise ratio from the signal; comparing the characteristic histogram moments with the measured optical signal-to-noise ratio; and determining, a proportion of non-linear noise if the comparison yields non-correspondence, wherein a relationship between the characteristic histogram moments and signal-to-noise ratio is determined using the following: where μ 0 and μ 1 are average values of the amplitude distribution of the logic “1's” and “0's”, σ 0 and σ 1 are standard deviations of the amplitude distribution of the logic “1's” and “0's”, OSNR is signal-to-noise ratio, <P> av is an average signal power, is an optical bandwidth, B el is an electrical bandwidth of a photodiode or an opto-electrical transducer, and =ηq/hv is detector sensitivity (η=quantum efficiency, q=elementary charge, h=quantum of action, v=frequency of the signal).