Francesco Alberti

Optimized link design for nonlinearity cancellation by optical phase conjugation

Nonlinear effects are one of the main causes of pulse degradation in high bit-rate transmission systems and several architectures have been proposed to compensate them by means of optical phase conjugation. In this letter, a new method to exploit an optical phase conjugator for nonlinearity cancellation is disclosed. The proposed method is simpler than those previously described in literature and allows a relevant improvement of systems performances. Link-design rules are analytically studied; moreover, their effectiveness is numerically demonstrated for different applications. This technique can apply to any bit rates and modulation formats.

40-Gb/s systems on G.652 fibers: comparison between periodic and all-at-the-end dispersion compensation

In the literature, two system solutions have been proposed to overcome high dispersion problems typical of G.652 fibers at high bit rates (40 Gb/s): they are periodic and all-at-the-end dispersion compensation. We carry out an exhaustive comparison between the two methods that, up to this moment, have been studied separately. In the first part, we introduce a simplified model on strong dispersion management (DM) with intrachannel four-waves mixing (IFWM) and intrachannel cross-phase modulation (IXPM). We then carry out extensive numerical simulations of a complete system in order to verify the results as a function of the input average power and of the input pulsewidth. Finally, we tackle a typical system aspect, i.e., the influence of nonlinear effects on dispersion compensating fibers (DCFs).

Techniques for nonlinearity cancellation into embedded links by optical phase conjugation

One of the main causes of signal degradation in high-bit-rate transmission systems is the interplay between fiber nonlinear effects and dispersion. Different techniques to compensate nonlinear effects in transmission systems, by using an optical phase conjugator, have been proposed in the literature. In this paper, two different innovative setups allowing nonlinearity cancellation in an embedded link are disclosed. The proposed schemes are simpler than those previously described and strongly improve systems performances. The physical mechanism allowing nonlinearity compensation is depicted, and the effectiveness of the proposed solutions is numerically demonstrated. Moreover a new practical method, useful for performance optimization of systems including a phase conjugator, is presented. Results apply to any bit-rate and modulation format.

Numerical and experimental comparison of dispersion compensation techniques on different fibers

The authors carry out a numerical and experimental comparison between three different techniques for chromatic dispersion compensation on a terrestrial 40-Gb/s system. They are: periodic dispersion compensation at the amplifier places; the same but with initial prechirp; and dispersion compensation all at the end of the system by means of highly dispersed pulses. Numerical results are consistent with experimental ones and suggest the most convenient compensation technique with respect to fiber type (G.652 or G.655) and pulsewidth (3-10 ps).

Experiments on 40 Gb/s Transmission with Wavelength Conversion: Results from the IST ATLAS Project

In this article we report the main experimental results obtained in the framework of the IST ATLAS project regarding the transmission at 40 Gb/s over long terrestrial links, including the frequency conversion of a signal. We report the single-channel 40 Gb/s transmission over a link 500 km long with an amplifier spacing of 100 km, both with G.652 fibers and G.653 fibers by periodically compensating the chromatic dispersion with dispersion-compensating fibers. We report the single-channel transmission at 40 Gb/s, also, after the wavelength conversion of a channel with both PPLN and semiconductor optical amplifier devices. In particular, 500 km distances are obtained with PPLN wavelength conversion and 300 km distances with semiconductor optical amplifiers. Some results have been reported for electronic devices operating at 40 Gb/s.

Towards transport networks based on 40 Gbit/s transmission: results from the IST ATLAS project

We report the main results from the IST ATLAS project on the transmission techniques for new network infrastructures. We report results on the transmission performance on 4/spl times/40 Gbit/s systems over a 500 km link, including wavelength conversion. We show that wavelength conversion based on a periodically poled lithium niobate (PPLN) device and systems based on N/spl times/40 Gbit/s are now fundamental elements for future transport networks.