Summary form only given. A schematic diagram of the experimental setup is shown. Sixteen channels in the S-band were transmitted over 3 spans of single mode fibre, for a total length of 280 km, using four dispersion-compensating S-band lumped Raman amplifiers. The S-band WDM signals were multiplexed and de-multiplexed with the C-band WDM signals at each repeater. The C-band erbium doped fiber amplifiers were operated in constant gain mode in order to minimize the tilt induced by the EDFAs.

The ACTS OPEN project aims at the assessment of the feasibility of an Optical Pan-European overlay Network (OPEN), interconnecting major European cities by means of a mesh of high-capacity optical fibre links cross-connected through transparent photonic nodes, making an extensive use of WDM for both transmission and networking. Two cross-border field trials have been scheduled to assess this concept: • The first one, linking Oslo in Norway (N) with Hjerring and Thisted in Denmark (Dk) via a mix of terrestrial (G.652) and submarine (G.653) types of fibre has been carried out from October to December 1997. • The second one, linking Paris in France (F) with Brussels in Belgium (B), via a terrestrial standard fibre cable will be initiated February 1998.

The time-space varying birefringence in single-mode optical fibers causes the polarization mode dispersion (PMD) to be a serious problem in high bit-rate transmissions. The PMD first- and second-order statistics are well known in the literature, but second-order PMD-induced pulse distortions have still to be clarified for sequences of pulses of arbitrary shape. We give, for the first time, the exact PMD time impulse response, up to second order. We show, both numerically and experimentally, that the effect of the rotation of the principal states of polarization (PSP) is to generate power overshoots on the "1" and "0" bit sequences.

We describe EDFFAs (Er-doped fluoride fiber amplifiers) and their design criteria, discuss the EDFFA gain-flatness control mechanism and new amplifier designs giving improved gain flatness, and present in detail system applications that have been explored in our laboratory. Among these are a study of EDFFA cascade in multichannel systems, and WDM transmission and routing systems using EDFFAs

The development of the information society will require the introduction of high-capacity transport networks with high performance and low cost. There are currently two ACTS (Advanced Communications Technologies and Services program launched by the European Commission) projects addressing specifically the problem of trans-European optical transport networks using WDM (wavelength division multiplexing). Important issues addressed are the high capacity transmission on existing fiber infrastructure and the introduction of flexibility in the network through the use of optical cross-connects. If these networks become a reality, they could drastically change the evolution of both telecommunication and computer networking because of their transparency and the abundance of inexpensive bandwidth.

This paper will present the results of the modelling and experimental activities carried out within the ACTS "OPEN" project to validate the feasibility of reconfigurable optical crossconnects to prepare on-coming field trials. Details of the crossconnect prototype implementation will also be given.

In conclusion, the natural variation of the link chromatic dispersion suppresses the sideband instability in transmission over transoceanic distances without in-line dispersion compensation. A transmission over 9000 km with 50-km amplifier spacing using terminal optical phase conjugation was numerically simulated yielding a Q factor of 12

This paper is an introduction to phase-shaped binary transmissions (PSBT), which allow to bridge more than 200 km in the linear regime over standard dispersive fibres. It also explains why duobinary transmissions did bridge up to 243 km. The spectral compression induced by the duobinary coding is not able to explain the impressive results obtained during recent experiments of optical phase-coded duobinary transmissions. We showed that the /spl Pi/ phase shift occurring in each "O" neighbouring a "1" allows the energy of the pulse over a longer distance in the "1" bit-time to be kept. This result has been confirmed analytically and numerically. The value of the optimal phase shift may vary depending on the rise- and fall-times of the phase modulation. We have named phase-shaped binary transmission (PSBT) on this principle.

Thirty-two 10-Gbit/s channels spaced by 100 GHz were transmitted over 500 km of dispersive fiber (D>+19 ps/nm.km) with 125-km amplifier spacing. This was made possible by the use of 3 in-line dual-stage, flat-gain Er-doped fibre amplifiers (EDFAs) incorporating dispersion-compensating fiber

We show experimentally and numerically that reducing the bandwidth of the sequence spectrum does not necessarily improve the propagation on a dispersive fibre. For instance an ideal duobinary coding-based transmission is strongly affected after only 65 km, while the conventional NRZ binary signal experiences a quite smaller penalty. However, adding only some small differences to this ideal case will not broaden the spectrum but may induce a dramatic improvement in the performance of the transmission. Therefore the spectrum bandwidth is not the relevant parameter to assess the transmission performance over a dispersive fibre.

The numerical and experimental design of the dispersion map is considered in dispersion-managed WDM N/spl times/10 Gbit/s wide-band transmission over distances larger than 500 km, with regard to nonlinear effects and SNR degradation.

Wavelength-division multiplexing (WDM) seems to be the most promising approach to achieve large throughput transmission over distances of a few hundred kilometers, and allows for optical networking functionalities. Several WDM transmission experiments over single mode fibre (SMF) were performed that showed very high throughput-distance products. The requirements on the stability of light sources, filters, and other optical components is such that a channel spacing of 200 GHz is emerging as a viable solution. We first investigate numerically the propagation of N×10 Gbit/s channels over SMF with dispersion management along the link. The channel separation is such that the entire band of fluoride-based EDFAs (EDFFAs), about 25 nm between 1536 and 1560 nm, is used in order to relax the requirements on optical components. The focus is on the impact of the dispersion map on the transmission performance. Finally, the results of a 16×10 Gbit/s dispersion-managed transmission experiment over more than 500 km of SMF, are compared to the theoretical findings

The numerical and experimental design of the dispersion map is considered in dispersion-managed WDM Nx10 Gbit/s wide-band transmission over distances larger than 500 km, with regard to nonlinear effects and SNR degradation.

16 10 Gbit/s channels spanning 24 nm were transmitted over 531 km of dispersive fibre with only seven fluoride-based EDFAs, amplifier spacing varied between 60 and 93 km, and optimised dispersion management using dispersion-compensating fibre was utilised.

The authors have shown numerically, and confirmed experimentally, that reducing the bandwidth of the sequence spectrum (as opposed to the pulse spectrum), for instance using a duobinary coding, does not necessarily improve the propagation through dispersive fibres.