Experimental demonstration of optical performance monitoring for RZ-DPSK signals using delay-tap sampling method

The emerging transparent optical networks, employing spectrally-efficient modulation formats require new methods for supervision of signal quality in the optical domain. In this paper we demonstrate the optical performance monitoring (OPM) of optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD) in return-to-zero differential phase-shift keying (RZ-DPSK) signals using asynchronous delay-tap sampling and pattern recognition algorithms. We experimentally show noise measurement of OSNR from 8.7 dB to 32 dB with low optical input power requirement. Moreover, residual CD can be evaluated in the range from -600 to +600 ps/nm. The results indicate that careful adjustment of delay is necessary in order to ensure accurate measurement.