Efficient generation and multiplexing of optical orbital angular momentum modes in a ring fiber by using multiple coherent inputs.

We propose an approach to efficiently generate and multiplex optical orbital angular momentum (OAM) modes in a fiber with a ring refractive index profile by using multiple coherent inputs from a Gaussian mode. By controlling the phase relationship of the multiple inputs, one can selectively generate OAM modes of different states l. By controlling both the amplitude and phase of the multiple inputs, multiple OAM modes can be generated simultaneously without additional loss coming from multiplexing. We show, by simulation, the generation of OAM modes (OAM state |l|<3) with mode purity greater than 99%. The power loss of generating and multiplexing seven modes is about 35%. A transmitter for an OAM-based mode-division multiplexing system is proposed based on the discrete Fourier transform between the data carried by the multiple inputs and the data carried by the OAM modes. The experimental implementation of the proposed approach could be achieved by integrating ring fiber, multicore fiber, and photonic integrated circuit technology.

Time-stretch oscilloscope with dual-channel differential detection front end for monitoring of 100 Gb/s return-to-zero differential quadrature phase-shift keying data.

Optical performance monitoring of high-capacity networks is one of the enabling technologies of future reconfigurable optical switch networks. In such networks, rapid performance evaluation of data streams becomes challenging due to the use of advanced modulation formats and high data rates. The time-stretch enhanced recording oscilloscope offers a potential solution to monitoring high-rate data in a practical time scale. Here we demonstrate an architecture with a differential detection front end for simultaneous I/Q data monitoring of a 100 gigabits/s return-to-zero differential quadrature phase-shift keying signal. This demonstration shows the potential of this technology for rapid performance monitoring of high-rate optical data streams that employ advanced modulation formats.

Experimental demonstration of packet-rate 10-Gb/s OOK OSNR monitoring for QoS-aware cross-layer packet protection.

A cross-layer network platform may enable introspective access to the physical layer, allowing optical performance monitoring measurements to feedback to higher layers for packet rerouting and protection. We experimentally demonstrate quality-of-service-aware packet protection that leverages cross-layer signaling based on the monitoring of packets' optical-signal-to-noise ratio. In order to detect degraded data streams, the monitoring system is based on a delay-line Mach-Zehnder interferometer and a field-programmable gate array. The system is realized in an experimental cross-layer enabled optical packet switched fabric, measuring the optical-signal-to-noise ratio for 10-Gb/s OOK streams. The packet protection scheme uses the dynamic performance measurements to actuate a rerouting of high-quality-of-service packets. 8 × 10-Gb/s wavelength-striped optical messages are rerouted through the fabric error-free (bit-error rates less than 10(-12)).

Optical monitoring of PMD accumulation on a Pol-MUX phase-modulated signal using degree-of-polarization measurements.

We experimentally demonstrate a chromatic dispersion insensitive monitoring technique for monitoring of polarization mode dispersion and time misalignment in a 80 Gbit/s polarization-multiplexed return-to-zero differential phase-shift-keying (Pol-MUX RZ-DPSK) signal using a polarimeter and degree-of polarization (DOP) measurements. This technique is modulation format independent (i.e., applicable to both the phase- and amplitude-modulated data) and capable of measuring the fast change of polarization effects caused by vibration or other fast disturbances in the fiber link. We show that the monitored DOP of this signal decreases by 10.8% with differential group delay of 0-12 ps and decreases by 20% with a maximum misalignment of 12.5 ps between two orthogonally polarized RZ-DPSK channels. These measurements are less sensitive to chromatic dispersion of 0-400 ps/nm.