Patent ID: 8611741

Claim:
A method for determining signal quality in a wavelength division multiplexing network comprising: formatting each of a plurality of communication channels so that a transmitted signal corresponding to each channel carries a distinct profile in time, wherein the distinct profile in time is equivalent to a distinct profile in frequency; multiplexing signals associated with a plurality of formatted communication channels onto a combined signal; amplifying the combined signal in a medium that adds amplified spontaneous emission to the combined signal to generate an amplified combined signal; converting a portion of the amplified combined signal into an electrical signal containing signal-spontaneous beat noise; extracting from the electrical signal a time-dependent waveform of the signal-spontaneous beat noise; deriving from the time-dependent waveform of the signal-spontaneous beat noise a first scalar parameter proportional to an optical signal to noise ratio of one of a plurality of multiplexed communication channels in the combined signal; and deriving from the time-dependent waveform of the signal-spontaneous beat noise a second scalar parameter proportional to the optical signal to noise ratio of one other of the plurality of multiplexed communication channels in the combined signal.