N Nicola Calabretta

Optical packet switching and buffering by using all-optical signal processing methods

We present a 1 /spl times/ 2 all-optical packet switch. All the processing of the header information is carried out in the optical domain. The optical headers are recognized by employing the two-pulse correlation principle in a semiconductor laser amplifier in loop optical mirror (SLALOM) configuration. The processed header information is stored in an optical flip-flop memory that is based on a symmetric configuration of two coupled lasers. The optical flip-flop memory drives a wavelength routing switch that is based on cross-gain modulation in a semiconductor optical amplifier. We also present an alternative optical packet routing concept that can be used for all-optical buffering of data packets. In this case, an optical threshold function that is based on a asymmetric configuration of two coupled lasers is used to drive a wavelength routing switch. Experimental results are presented for both the 1 /spl times/ 2 optical packet switch and the optical buffer switch.

Wavelength conversion using nonlinear polarization rotation in a single semiconductor optical amplifier

We discuss an all-optical wavelength converter based on nonlinear polarization rotation in a single semiconductor optical amplifier. We show that inverted and noninverted wavelength conversion can be realized. We also demonstrate this wavelength-conversion concept can operate over a large wavelength range. Experiments show that error-free wavelength conversion can be obtained at a bit rate of 10 Gb/s.

Optical signal processing based on self-induced polarization rotation in a semiconductor optical amplifier

We demonstrate novel optical signal processing functions based on self-induced nonlinear polarization rotation in a semiconductor optical amplifier (SOA). Numerical and experimental results are presented, which demonstrate that a nonlinear polarization switch can be employed to achieve all-optical logic. We demonstrate an all-optical header processing system, an all-optical seed pulse generator for packet synchronization, and an all-optical arbiter that can be employed for optical buffering at a bit rate of 10 Gb/s. Experimental results indicate that optical signal processing functions based on self-polarization rotation have a higher extinction ratio and a lower power operation compared with similar functions based on self-phase modulation.

All-optical packet/circuit switching-based data center network for enhanced scalability, latency, and throughput

Applications running inside data centers are enabled through the cooperation of thousands of servers arranged in racks and interconnected together through the data center network. Current DCN architectures based on electronic devices are neither scalable to face the massive growth of DCs, nor flexible enough to efficiently and cost-effectively support highly dynamic application traffic profiles. The FP7 European Project LIGHTNESS foresees extending the capabilities of todays electrical DCNs throPugh the introduction of optical packet switching and optical circuit switching paradigms, realizing together an advanced and highly scalable DCN architecture for ultra-high-bandwidth and low-latency server-to-server interconnection. This article reviews the current DC and high-performance computing (HPC) outlooks, followed by an analysis of the main requirements for future DCs and HPC platforms. As the key contribution of the article, the LIGHTNESS DCN solution is presented, deeply elaborating on the envisioned DCN data plane technologies, as well as on the unified SDN-enabled control plane architectural solution that will empower OPS and OCS transmission technologies with superior flexibility, manageability, and customizability.

Novel flat datacenter network architecture based on scalable and flow-controlled optical switch system

We propose and demonstrate an optical flat datacenter network based on scalable optical switch system with optical flow control. Modular structure with distributed control results in port-count independent optical switch reconfiguration time. RF tone in-band labeling technique allowing parallel processing of the label bits ensures the low latency operation regardless of the switch port-count. Hardware flow control is conducted at optical level by re-using the label wavelength without occupying extra bandwidth, space, and network resources which further improves the performance of latency within a simple structure. Dynamic switching including multicasting operation is validated for a 4 x 4 system. Error free operation of 40 Gb/s data packets has been achieved with only 1 dB penalty. The system could handle an input load up to 0.5 providing a packet loss lower that 10(-5) and an average latency less that 500 ns when a buffer size of 16 packets is employed. Investigation on scalability also indicates that the proposed system could potentially scale up to large port count with limited power penalty.

Ultrafast asynchronous multioutput all-optical header processor

We present a novel all-optical header processing technique that can be utilized in all-optical packet switches. The header processor consists of a terahertz optical asymmetric demultiplexer in combination with a header preprocessor that separates the packet header from the packet payload. Experimental results show asynchronous operation of the header processor at a header bit rate of 10 Gb/s in the case of two output ports. This concept can, however, be extended to a larger number of output ports, operates at low power, and allows photonic integration.

Three-state all-optical memory based on coupled ring lasers

An all-optical memory with three states is presented. The memory is realized from three coupled ring lasers. The state of the optical memory is determined by the wavelength of the memorys output light. In each state, only one wavelength is dominant. The three-state all-optical memory can be utilized in all-optical packet switches. The concept of the memory is explained and experimental results are presented that demonstrate that a contrast ratio larger than 40 dB between output states of the memory can be obtained.

Monolithically Integrated InP 1

The static and dynamic characteristics of a monolithically integrated InP 1 × 16 optical phased-array switch are presented. The device demonstrates static switching with an average extinction ratio of 18.6 dB, on-chip loss below 7 dB, and wavelength dependence of less than 0.8 dB in the entire C-band. A 40-Gb/s nonreturn-to-zero signal is transmitted through the switch with a power penalty below 0.4 dB. Using a programmable electronic circuit, dynamic switching to all 16 outputs is achieved with response times less than 11 ns.

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Optical packet switches that scale to thousands of input/output ports might find their application in next-generation datacenters (DCs). They will allow interconnecting the servers of a DC in a flat topology, providing higher bandwidth and lower latency in comparison with currently applied electronic switches. Using a simple analytic model that allows computing end-to-end latency and throughput, we show that optical interconnects that employ a centralized (electronic) controller cannot scale to thousands of ports while providing end-to-end latencies below 1 μs and high throughput. We therefore investigate architectures with highly distributed control. We present astrictly non-blocking wavelength division multiplexing architecture with contention resolution based on wavelength conversion. We study the packet loss probability of such architecture for different implementations of the contention resolution functionality. Furthermore, we show that the proposed architecture, applied in a short link with flow control, provides submicrosecond end-to-end latencies and allows high load operation, while scaling over a thousand ports.

16 Optical Switch With Wavelength-Insensitive Operation

In this study, we demonstrate error-free all-optical wavelength conversion of ultrahigh-speed intensity modulated signals by means of four-wave mixing in a quantum-dot semiconductor optical amplifier. Error-free performance at a bit rate of 320 Gbit/s is measured for the extracted 40 Gbit/s tributaries with a 3.4 dB average power penalty to the original signal.