Monitoring of optical signals from constellation diagrams measured with linear optical sampling

Linear optical sampling detects samples of the electric field of an optical waveform using its interference with a train of sampling pulses. This allows statistical electric field characterization, for example the measurement of a constellation diagram in the complex plane. From such information, one can directly track impairments that affect the phase and more generally the electric field of a data-encoded telecommunication channel. Constellation diagrams are measured at 10 Gb/s using a waveguide implementation of linear optical sampling. The intensity and phase fluctuations at a given position in the bit slot are quantified in various situations typically met in optical networks. The properties of various data modulation schemes for phase shift keying are investigated, and the noise induced by ASE on the electric field is directly quantified. Finally, a direct measurement of the Gordon-Mollenauer nonlinear phase noise is performed.