Giampiero Contestabile

Multiple wavelength conversion for WDM multicasting by FWM in an SOA

Using multipump four-wave mixing in a semiconductor optical amplifier, we demonstrate a simple scheme for multicasting an input nonreturn-to-zero 10-Gb/s signal to six different output wavelengths, all compliant with a 200-GHz channel grid. The signals are successfully transmitted in a metro-like system.

1.28 terabit/s (32x40 Gbit/s) wdm transmission system for free space optical communications

We review a novel free space optical (FSO) system that represents a significant breakthrough in the area of FSO communications. The system encompasses a pair of novel terminals: these allow direct and transparent optical connection to common single mode fibers and include a dedicated electronic control unit that effectively tracks the signal beam wandering due to atmospheric turbulence and mechanical vibrations. Further improvement in the signal power stabilization is achieved by means of saturated EDFAs. These solutions allow to realize a new FSO system, which is tested in a double-pass FSO link between two buildings in Pisa, Italy. When the terminals are fed by common WDM signals they allow enough power budget and margins to support a record high capacity transmission (32times40 Gbit/s), with a enormous improvement of stability (six hours with no error burst). During day-long transmission, the system behavior has been deeply characterized to correlate any increase of bit error ratio (BER) to the FSO control parameters.

Double-stage cross-gain modulation in SOAs: an effective technique for WDM multicasting

We experimentally demonstrate an optical circuit capable of multiwavelength conversion. The circuit structure is intrinsically stable and polarization independent. It may thus be a practical solution for wavelength-division multiplexing multicasting applications. Its working principle relies on synchronous double-stage cross-gain modulation in SOAs between an incoming data-modulated signal and several local continuous wave lasers. We report the simultaneous wavelength conversion of an input 10Gb/s nonreturn-to-zero to eight 200-GHz-spaced output channels. The obtained signals show only a moderate optical signal-to-noise ratio penalty.

Cross-Gain Compression in Semiconductor Optical Amplifiers

In this paper, we present a novel scheme that exploits cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs) without overall pattern effects. This technique uses two signals with reversed-intensity modulation and different wavelength to exploit propagation and gain-compression dynamics in gain-saturated SOAs at almost constant overall input power. The resulting cross-gain-compression mechanism between copropagating waves can lead to all-optical waveform reshaping. By using this technique, we experimentally demonstrate enhanced wavelength conversion by XGM and wavelength-preserving noise compression at 10 Gb/s

Single and multicast wavelength conversion at 40 Gb/s by means of fast nonlinear polarization switching in an SOA

We experimentally demonstrate all-optical wavelength conversion of a 40-Gb/s nonreturn-to-zero signal by means of nonlinear polarization switching in a single semiconductor optical amplifier (SOA). Using a highly nonlinear SOA optimized for very fast gain recovery time, we observe no appreciable penalty for the conventional (single) wavelength conversion. We also obtain, for the first time by using this technique, the simultaneous multiconversion to different wavelengths (four on a 200-GHz frequency grid) of an input signal.

40-GHz all-optical clock extraction using a semiconductor-assisted fabry-Pe/spl acute/rot filter

We obtain 40-Gb/s all-optical clock recovery by means of a very simple scheme. We use a high finesse low-loss Fabry-Pe/spl acute/rot filter and a semiconductor optical amplifier acting as an amplitude equalizer. The recovered clock signal shows large locking range, low amplitude fluctuation, and limited time jitter.

Polarization and wavelength-independent time-division demultiplexing based on copolarized-pumps FWM in an SOA

A novel optical time-division demultiplexer based on copolarized-pumps four-wave mixing in semiconductor optical amplifiers is presented. The scheme is polarization and wavelength independent. Effective 10-Gb/s channel extraction from an optical time-division multiplexed 40-Gb/s aggregate frame is experimentally demonstrated.

A Bidirectional WDM/TDM-PON Using DPSK Downstream Signals and a Narrowband AWG

We present an innovative architecture to realize a single feeder bidirectional amplified wavelength-division-multiplexing/time-division-multiplexing passive optical network based on modified nonreturn-to-zero differential phase-shift keying (DPSK) downstream signals at 20 Gb/s and a narrowband arrayed waveguide grating (AWG). The AWG plays at the same time the role of channel distributor, simultaneous demodulator for all DPSK channels, and eliminates the need for chromatic dispersion compensation. A saturated semiconductor optical amplifier (SOA) provides bidirectional amplification to compensate the splitter losses. The remodulated upstream signals are obtained at 1 Gb/s by means of a reflective SOA. Experimental results show error-free operation on both downstream and upstream signal.

Efficiency flattening and equalization of frequency up- and down-conversion using four-wave mixing in semiconductor optical amplifiers

We show that four-wave mixing in semiconductor optical amplifiers with the use of two orthogonally polarized pumps offers the possibility of frequency conversion with constant efficiency over several terahertz. The same two-pump configuration permits one to convert the signal to lower or higher frequencies with the same efficiency.

Enhancing Resilience to Rayleigh Crosstalk by Means of Line Coding and Electrical Filtering

We demonstrate a technique that ameliorates the performance of bidirectional systems impaired by in-band Rayleigh crosstalk, which is common in passive optical access networks based on centralized remote wavelength feeding. The technique is based on the combined use of a suitable line coding and ad hoc postdetection electrical filtering. Therefore, it can be seamless implemented in optical access systems and it is easily scalable with the data rate. We experimentally assess the technique by using a 8B10B coded 1.25-Gb/s signal. We report an increased tolerance to the signal-to-crosstalk ratio by about 5 dB.