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. We also explored and studied different monitor parameters, including the shape of the filter spectrum, the bandwidth of the filter, DLI delay, and DLI phase-detuning to determine the design guidelines for a desired level of accuracy for the OSNR monitor in an optical network.

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. We reconfigured the system to perform separate simultaneous correlation (data pattern recognition), equalization, and modulation format conversion on four and eight WDM binary/quadrate phase-shift keyed channels at 26 and 20 Gbaud, respectively. The aggregate throughput of 416 Gb/s is achieved.