Piero Gambini

Transparent optical packet switching: the European ACTS KEOPS project approach

This paper reviews the work carried out under the European ACTS KEOPS (KEys to Optical Packet Switching) project, centering on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. The adopted approach uses optical packets of fixed duration with low bit rate headers to facilitate processing at the network/node interfaces. The paper concentrates on the networking concepts developed in the KEOPS project through a description of the implementation issues pertinent to optical packet switching nodes and network/node interfacing blocks, and consideration of the network functionalities provided within the optical packet layer. The implementation, from necessity, relies on advanced optoelectronic components specifically developed within the project, which are also briefly described.

Transparent optical packet switching: network architecture and demonstrators in the KEOPS project

This paper reviews the work carried out in the ACTS KEOPS (Keys to Optical Packet Switching) project, describing the results obtained to date. The main objective of the project is the definition, development, and assessment of optical packet switching and routing networks, capable of providing transparency to the payload bit rate, using optical packets of fixed duration and low bit rate headers in order to enable easier processing at the network/node interfaces. The feasibility of the KEOPS concept is assessed by modeling, laboratory experiments, and testbed implementation of optical packet switching nodes and network/node interfacing blocks, including a fully equipped demonstrator. The demonstration relies on advanced optoelectronic components, developed within the project, which are described.

Synchronisation Issues in Optical Packet Switched Networks

This paper provides an analysis on the synchronisation aspects in optical packet switched networks. Solutions that have been developed in the framework of the European ACTS KEOPS project are proposed.

State of the Art of Photonic Packet Switched Networks

A review of the status of research in the field of guided wave photonic packet switched networks is presented. Network configurations and packet formats proposed so far are described, as well as techniques for routing, contention resolution and packet synchronization in the switching nodes.

Performance assessment of a photonic ATM switch based on a wavelength-controlled fiber loop buffer

Summary form only given. We report the first BER measurement of a photonic switch based on a wavelength-controlled fiber loop buffer, in real operation, i.e., with computer-generated repeated random input traffic, with all interfering and noise sources. Further measurements will be carried out in the near future and compared to a simulation model, regarding the influence of wavelength crosstalks, number of circulations, and wavelength allocation.

Frequency stabilization of DFB laser diodes to the P(3) line of acetylene at 1.52688 μm by external phase modulation

The emission frequency of DFB laser diodes has been locked to the P(3) line of the roto- vibrational absorption spectrum of Acetylene at 1526.878 nm. An external phase modulator is used to obtain the error signal, thus resulting in absence of frequency modulation on the frequency stabilized output, as well as good short and long term stability. The stability has been evaluated analyzing the beat signal between two independently stabilized lasers.

Performance and limitations of laser diodes stabilized to the sides of molecular absorption lines of ammonia

Performance and limitations of laser frequency stabilization based on the locking to the side of an absorption line are discussed: experimental results of spectroscopic measurements and of the stabilization of 1543‐nm DFB laser diodes to ammonia absorption lines are presented.

Impact of DFB-LD FM response distortion, in amplitude and phase, on FSK coherent systems

The influence of amplitude and phase distortions of the FM response of DFB (distributed feedback) lasers on coherent FSK (frequency shift keying) transmission systems has been investigated. It was found that pattern effects are mainly due to phase distortions, while the IF (intermediate frequency) spectrum broadening is due to both amplitude and phase distortions. Possible remedies are described, including device selection, line coding, and phase and/or amplitude equalization of the FM response. A comparison between observed spectra and computer analysis has been performed, showing a good agreement. Transmission experiments at 140 Mb/s have been carried out, showing the predicted effects on the eye diagram.<<ETX>>

Laser frequency stabilization for high bit-rate FSK multichannel coherent systems

After reviewing some previously proposed laser frequency stabilization techniques for multichannel coherent systems, the authors present a simple, alternative method, making use of a scanning Fabry-Perot resonator. This technique, which proved effective in a preliminary experiment stabilizing a single DFB (distributed feedback) laser diode within less than 500 kHz, was successfully applied to the collective stabilization of a two-channel transmitter and can be easily extended to a multichannel configuration with a high number of channels. The same principle can operate, with some modification, in the presence of FSK (frequency shift keying) direct modulation. This has been experimentally demonstrated for a DFB laser that was directly modulated up to 2 Gb/s.<<ETX>>

Demonstration of polarisation independent coherent transmission by synchronous intra-bit polarisation spreading

Polarization-independent heterodyne detection of an FSK (frequency shift keying) signal has been demonstrated by the synchronous intrabit polarization spreading technique, which consists in the switching or proper modulation of the state of polarization of the laser output field inside the bit period. This approach is particularly suitable for distribution networks, as the polarization diversity function is shifted to the transmitter, thus resulting in a simpler and cheaper heterodyne receiver. A transmission experiment, making use of a 1.55 mu m DFB (distributed feedback) laser diode, directly FSK modulated at 155 Mb/s, a properly developed high-speed polarization modulator, and single filter heterodyne detection, has been successfully carried out. The penalty resulting from preliminary bit-error-rate measurements ranges from 4 to 6.5 dB, including the 3 dB intrinsic loss common to all polarization spreading techniques.<<ETX>>