Experimental demonstration of robustness and accuracy of a DLI-based OSNR monitor under changes in the transmitter and link for different modulation formats and baud rates.

We experimentally studied the performance of a delay-line interferometer-based optical signal-to-noise ratio (OSNR) monitor that is pre-calibrated in optimal conditions for 25-Gbaud pol-muxed quadrature-amplitude-modulation (QAM) signals, when unpredicted changes outside the monitor occurred either in the transmitter or the link.

Demonstration of all-optical phase noise suppression scheme using optical nonlinearity and conversion/dispersion delay.

We propose and demonstrate an all-optical phase noise reduction scheme that uses optical nonlinear mixing and tunable optical delays to suppress the low-speed phase noise induced by laser linewidth. By utilizing the phase conjugate copy of the original signal and two narrow-linewidth optical pumps, the phase noise induced by laser linewidth can be reduced by a factor of ∼5 for a laser with 500-MHz phase noise bandwidth. The error-vector-magnitude can be improved from ∼30% to ∼14% for the same laser linewidth for 40-Gbit/s quadrature phase shift keying signal.

Demonstration of in-service wavelength division multiplexing optical-signal-to-noise ratio performance monitoring and operating guidelines for coherent data channels with different modulation formats and various baud rates.

We demonstrated a delay-line interferometer (DLI)-based, optical-signal-to-noise ratio (OSNR) monitoring scheme of 100  Gbit/s polarization multiplexed quadrature-phase-shift-keying (PM-QPSK) four-channel WDM at 50-GHz International Telecommunication Union (ITU) grid with <0.5  dB error for signals with up to 26 dB of actual OSNR. We also demonstrated data format transparency and baud rate tunability of the OSNR monitor by measuring the OSNR for a 200  Gbit/s PM-16-QAM (25-Gbaud) signal and a 200  Gbit/s PM-QPSK (50-Gbaud) signal.

Simultaneous and independent processing of multiple input WDM data signals using a tunable optical tapped delay line.

We demonstrate a tunable optical tapped delay line that can simultaneously and independently operate on multiple wavelength-division multiplexed (WDM) data signals. The system utilizes the wavelength-dependent speed of light, together with nonlinear wavelength conversion stages. A phase-preserving scheme enables coherent addition of the weighted taps.