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Dense wavelength division multiplexing (DWDM) is the key technology for future data transport. It combines transmission of data rates up to several Tb/s [1] with an overall transparency to data format and bit rate. The expected huge bandwidth demand in the near future requires an adaptability of DWDM transmission technology to metropolitan networks. Therefore, dynamically configurable DWDM transmission technology for bit rates up to 10 Gb/s has been investigated in a field trial in Berlin. This field trial is part of the KomNet research project. It is the goal of this field trial to optimize DWDM systems to metropolitan network requirements. Several aspects are in this paper: (i) A network simulation tool is described which helps to enlighten the profitability of statically and dynamically configured network nodes. (ii) A newly developed technology to add and drop single-wavelength channels is explained. (iii) The scalability of the approach is demonstrated with an aggregate capacity of 0.8 Tb/s. The equipment has already been installed in the field and is ready for experiments.

Cross-phase modulation (XPM) is a major performance-limiting effect in high bit-rate wavelength-division-multiplexed (WDM) networks with narrow channel spacing. In this paper, we present closed expressions for fast and accurate calculation of both XPM-induced amplitude and phase distortions of WDM channels. This is of particular importance for network optimization and examination of advanced modulation formats. By comparison with simulations, we demonstrate the wide application range of the novel method.

Currently existing dense wavelength division multiplexing (DWDM) networks start to migrate from numerous point-to-point links towards meshed, transparent, optical networks with dynamically routed light paths. This increases the need for appropriate network monitoring and supervision methods. Optical performance monitoring (OPM) has to be cost-effective. Thus additional spendings for OPM have to be significantly smaller than the savings in OPEX due to increased reliability and ease of operation, administration, and maintenance (OAM). We elaborate on different advanced monitoring concepts. First, we discuss general failure scenarios in meshed networks. Then we describe software based failure root cause analysis and its implementation. We conclude that by implementing appropriate software algorithms in the network hardware effort can be significantly reduced. Finally, we assess different advanced OPM methods which may show up as useful to enable OPM in future optical networks.

We report on experimental results of optical performance monitoring (OPM) in a transparent optical network transmitting channels modulated at 10 Gb/s. This experiment was performed in an entirely field installed DWDM ring network (DWDM ring capacity: 80/spl times/10 Gb/s) with configurable optical add drop multiplexers (OADMs) at different locations within the city of Berlin, Germany.

In this paper we present concepts and field trails of automatically switched DWDM networks (ASON). One test network was part of the German field trial "KomNet". The other network is developed and will be tested in the "CAPRICORN" project, a project in the framework of IST (European Community). We focus our investigations on the photonic layer and show results of our experiments on the performance of the network control plane. Each testbed consists of 4 optical cross connects (OXC) in an optically meshed network configuration for the metropolitan and regional area. The main goals are to demonstrate in the field an optical network managed by a control plane and to investigate the functionality of automatically switched transparent optical networks.

In this paper we present the topology of an optically transparent DWDM network testbed (part of the KomNet field-trial). We show results of our investigation on performance monitoring in the optical layer of this complex network. The testbed consists of a remotely configurable DWDM metropolitan area ring network (capable of transport up to 80x10 Gb/s) with two OADMs and one HUB/OXC and a long-haul bi-directional DWDM link (16x10 Gb/s, 8 spans over 750 km).

We report on error-free multiclient transmission over a Germany-wide all-optical, configurable DWDM system. The performance of the transparent connection of a metropolitan area network and a bi-directional long haul system is investigated under real-world conditions. We report on the topology of SIEMENS part of the Germany-wide field trial KOMNET and results of transparent interconnections between different optical domains.

Injection of electron-hole pairs into the surface-space-charge layer of doped semiconductors leads to an acceleration of the generated carriers following the electrostatic field in the surface depletion region. The electrons and holes move into opposite directions, thus reducing the driving force by building up an opposite electric field. As a consequence of the carrier seperation, the sign of the resulting electric field in the surface depletion zone changes and the carriers are driven back until the sign changes again. This process of an altering resulting electric field gives rise to a coherent oscillation of the carriers within the time scale of momentum relaxation (ballistic regime). The oscillation amplitude of the holes should be much smaller than that of the electrons because of their larger mass. This scenario is expected only for weak scattering, momentum relaxation of the carriers leads to damping of the oscillation.

A compact optical performance monitor for dense wavelength division multiplex networks is presented. This novel low-cost device can be used to assess the signal quality in terms of the Q-factor independently of data format and line rate.