Dimitris Tsiokos

IST-LASAGNE: towards all-optical label swapping employing optical logic gates and optical flip-flops

The Information Society Technologies-all-optical LAbel SwApping employing optical logic Gates in NEtwork nodes (IST-LASAGNE) project aims at designing and implementing the first, modular, scalable, and truly all-optical photonic router capable of operating at 40 Gb/s. The results of the first project year are presented in this paper, with emphasis on the implementation of network node functionalities employing optical logic gates and optical flip-flops, as well as the definition of the network architecture and migration scenarios.

10-Gb/s all-optical half-adder with interferometric SOA gates

In this letter, we report an all-optical module that generates simultaneously four Boolean operations at 10 Gb/s. The circuit employs two cascaded ultrafast nonlinear interferometers and requires only two signals as inputs. The first gate is configured as a 2 /spl times/ 2 exchange-bypass switch and provides OR and AND logical operations. The second gate generates XOR (SUM bit) and AND (CARRY bit) Boolean operations and constitutes a binary half-adder. Successful operation of the system is demonstrated with 10-Gb/s return-to-zero pseudorandom data patterns.

40-Gb/s All-Optical Processing Systems Using Hybrid Photonic Integration Technology

This paper presents an experimental performance characterization of all-optical subsystems at 40 Gb/s using interconnected hybrid integrated all-optical semiconductor optical amplifier (SOA) Mach-Zehnder interferometer (MZI) gates and flip-flop prototypes. It was shown that optical gates can be treated as generic switching elements and, when efficiently interconnected, can form larger and more functional network subsystems. Specifically, this paper reports on all-optical subsystems capable of performing on-the-fly packet clock recovery, 3R regeneration, label/payload separation, and packet routing using the wavelength domain. The all-optical subsystems are capable of operating with packet-mode traffic and are suitable for all-optical label-switched and self-routed network nodes. The intelligent functionality offered, combined with the compactness and stability of the optical gates, verifies the potential that all-optical technology can find application in future data-centric networks with efficient and dynamic bandwidth utilization. This paper also reports on the latest photonic integration breakthroughs as a potential migration path for reducing fabrication cost by developing photonic systems-on-chip utilizing multiple SOA-MZI optical gates on a single chip

Clock and data recovery circuit for 10-Gb/s asynchronous optical packets

We demonstrate an all-optical clock and data recovery circuit for short asynchronous data packets at 10-Gb/s line rate. The technique employs a Fabry-Perot filter and a SOA-based ultrafast nonlinear interferometer (UNI) to generate the local packet clock, followed by a second UNI gate to act as decision element, performing a logical AND operation between the extracted clocks and the incoming data packets. The circuit can handle short packets arriving at time intervals as short as 1.5 ns and arbitrary phase alignment.

All-Optical 3R Burst-Mode Reception at 40 Gb/s Using Four Integrated MZI Switches

We demonstrate an all-optical retime, reshape, reamplify (3R) burst-mode receiver (BMR) operating error-free with a 40-Gb/s variable-length asynchronous optical data packets that exhibit up to 9-dB packet-to-packet power variation. The circuit is completely based upon hybrid integrated Mach-Zehnder interferometric (MZI) switches as it employs four cascaded MZIs, each one performing a different functionality. The 3R burst-mode reception is achieved with the combination of two discrete all-optical subsystems. A reshape, reamplify BMR employing a single MZI is used first to perform power equalization of the incoming bursts and provide error-free data reception. This novel approach is experimentally demonstrated to operate error-free, even for a 9-dB dynamic range of power variation between bursty data packets and for a wide range of average input power. The obtained power-equalized data packets are then fed into a 3R regenerator to improve the signal quality by reducing the phase and amplitude jitter of the incoming data. This packet-mode 3R regenerator employs three MZIs that perform wavelength conversion, clock extraction, and data regeneration for every packet separately and operates at 40 Gb/s, exhibiting rms timing jitter reduction from 4 ps at the input to 1 ps at the output and a power penalty improvement of 2.5 dB

Pulse repetition frequency multiplication with spectral selection in Fabry-Perot filters

We present methods for obtaining high-repetition-rate full duty-cycle RZ optical pulse trains from lower rate laser sources. These methods exploit the memory properties of the Fabry-Perot filter for rate multiplication, while amplitude equalization in the output pulse train is achieved with a semiconductor optical amplifier or with a second transit through the Fabry-Perot filter. We apply these concepts to experimentally demonstrate rate quadruplication from 10 to 40 GHz and discuss the possibility of taking advantage of the proposed methods to achieve repetition rates up to 160 GHz.

Client-weighted medium-transparent MAC protocol for user-centric fairness in 60 GHz radio-over-fiber WLANs

We present a novel client-weighted mediumtransparent medium access control (CW-MT-MAC) protocol with enhanced fairness service delivery properties accompanied by a low-loss remote access unit (RAU) architecture for use in indoor, Gbps-capable, 60 GHz radio-over-fiber (RoF) wireless local area networks (WLANs). Our approach relies on incorporating a client-weighted algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as to distribute the available wavelengths to the different antenna units according to the total number of active users served by each individual antenna. The protocols throughput and delay fairness characteristics are evaluated and validated through both simulations and analytic modeling for saturated network traffic operational conditions. In addition, extended simulation-based performance analysis for nonsaturated network conditions and for different end-user distributions, traffic loads, and available optical wavelengths at 1 Gbps data rates is presented. Our results confirm that complete throughput equalization can be achieved even for highly varying user population patterns when certain wavelength availability conditions are satisfied. At the same time, the presented scheme manages to equalize the average packet delays amongst packets generated by all RAUs while concurrently dropping the packet delay variation metric that is essential for quality of service delivery. Finally the proposed RAU design reduces insertion losses by almost 14 dB compared to RAU elements used in MT-MAC-compatible bus networks, extending in this way the number of supported RAUs by an order of magnitude and enabling the formation of extended-reach, high-speed RoF WLANs.

Column Address Selection in Optical RAMs With Positive and Negative Logic Row Access

An optical RAM row access gate followed by a column address selector for wavelength-division-multiplexing (WDM)-formatted words employing a single semiconductor optical amplifier-Mach-Zehnder interferometer (SOA-MZI) is presented. RAM row access is performed by the SOA-MZI that grants random access to a 4-bit WDM-formatted optical word employing multiwavelength cross-phase-modulation (XPM) phenomena, whereas column decoding is carried out in a completely passive way using arrayed waveguide grating. Proof-of-concept experimental verification for both positive and negative logic access is demonstrated for 4 × 10 Gb/s optical words, showing error-free operation with only 0.4-dB-peak-power penalty and requiring a power value of 25 mW/Gb/s.

Repetition rate upgrade for optical sources

A novel method for the multiplication of the repetition rate of full duty-cycle return-to-zero optical sources is presented. It employs the memory property of a Fabry-Perot filter for the multiplication task, combined with the gain saturation of a semiconductor optical amplifier for amplitude equalization. This concept has been applied to quadruplicate the rate of a distributed feedback laser source operating at 10 GHz.

Digital Optical Physical-Layer Network Coding for mm-Wave Radio-Over-Fiber Signals in Fiber-Wireless Networks

We demonstrate a digital Optical Physical-layer Network Coding (OPNC) for mm-wave fiber-wireless signals modulated with up to 2.5 Gb/s On/OFF Keyed (OOK) data. The proposed OPNC concept uses an all-optical XOR gate comprising a Semiconductor Optical Amplifier-Mach Zehnder Interferometer (SOA-MZI) with SOAs being driven at low moderate electrical currents in order to perform the all-optical encoding between the OOK envelopes of the data, ignoring the high-frequency Sub-Carrier (SC) signal. In this scheme, network coding is performed on-the-fly at the central office and the resultant packet is broadcasted at the client nodes, where the decoding takes place. We demonstrate experimental results of OPNC using OOK data signals modulated on a 10 GHz SC with the aid of a second all-optical XOR gate for the decoding process at the clients site, reporting error-free performance for both synchronous/asynchronous data packets. The scenario of all optical encoding for 60 GHz SC frequencies followed by electrical decoding at the end-users is evaluated via PHY-layer simulations. Going a step further and considering the network level, we present a performance improvement on the network throughput by using the proposed network coding.