Patent ID: 8594499

Claim:
A method of monitoring phase nonlinearities of an optical communications system, the method comprising steps of: generating a test signal using a data signal transmitted through at least a portion of the optical communications system and received at a selected monitoring point of the optical communications system, the test signal comprising the received data signal and including a predetermined property that is uniquely associated with at least one phase nonlinearity of the optical communications system; and detecting the predetermined property of the test signal at the selected monitoring point; wherein the step of generating the test signal comprises steps of: transmitting a probe signal through a first wavelength channel of the optical communications system, the probe signal having a predetermined frequency and transition time; and transmitting the data signal through a second wavelength channel of the optical communications system, such that the test signal is generated by cross-phase modulation (XPM)-induced distortion of the data signal; wherein the predetermined property comprises a phase jitter of the test signal at a timing of self-phase modulation (SPM)-induced distortions of the probe signal arriving at the selected monitoring point.