Chirp management in silicon-graphene electro absorption modulators.

We study the frequency chirp properties of graphene-on-silicon electro-absorption modulators (EAMs). By experimentally measuring the chirp of a 100 µm long single layer graphene EAM, we show that the optoelectronic properties of graphene induce a large positive linear chirp on the optical signal generated by the modulator, giving rise to a maximum shift of the instantaneous frequency up to 1.8 GHz. We exploit this peculiar feature for chromatic-dispersion compensation in fiber optic transmission thanks to the pulse temporal lensing effect. In particular, we show dispersion compensation in a 10Gb/s transmission experiment on standard single mode fiber with temporal focusing distance (0-dB optical-signal-to-noise ratio penalty) of 60 km, and also demonstrate 100 km transmission with a bit error rate largely lower than the conventional Reed-Solomon forward error correction threshold of 10-3.

InP monolithically integrated coherent transmitter.

A novel InP monolithically integrated coherent transmitter has been designed, fabricated and tested. The photonic integrated circuit consists of a distributed Bragg reflector laser and a modified nested Mach-Zehnder modulator having tunable input power splitters. Back-to-back coherent transmission for PDM-QPSK signals is reported up to 10 Gbaud (40 Gb/s) using the integrated laser and up to 32Gbaud (128 Gb/s) using an external low phase noise laser.

Ultra-broad band, low power, highly efficient coherent wavelength conversion in quantum dot SOA.

We report broadband, all-optical wavelength conversion over 100 nm span, in full S- and C-band, with positive conversion efficiency with low optical input power exploiting dual pump Four-Wave-Mixing in a Quantum Dot Semiconductor Optical Amplifier (QD-SOA). We also demonstrate by Error Vector Magnitude analysis the full transparency of the conversion scheme for coherent modulation formats (QPSK, 8-PSK, 16-QAM, OFDM-16QAM) in the whole C-band.

All-optical 40 Gbits/s packet regeneration by means of cross-gain compression in a semiconductor optical amplifier.

We experimentally demonstrate all-optical reshaping of 40 Gbits/s packets by using cross-gain compression in a semiconductor optical amplifier (SOA). This scheme, which is based on cross-saturation effects between two conjugate signals copropagating in a single SOA, is wavelength preserving and polarization independent and does not suffer from any transient effect at packet edges. We report evidence of noise redistribution and packet reshaping by means of the bit-error rate versus threshold measurements for different input optical signal-to-noise ratios.

A simple and low-power optical limiter for multi-GHz pulse trains.

We study the limiting-amplification capability of a saturated Semiconductor Optical Amplifier (SOA) followed by an optical band-pass filter. We experimentally demonstrate that this simple optical circuit can be effectively exploited to realize a low-power optical limiter for amplitude-modulated pulse trains at multi-GHz repetition rate. We report very large amplitude-modulation-reduction factors for the case of 20 and 40 GHz pulse trains that are super-imposed with modulating frequencies ranging from 100kHz to several GHz.

[A comparison between antigliadin antibodies and blood xylose in celiac disease]. / Comparazione tra anticorpi antigliadina e xilosemia nella malattia celiaca.

We have compared serum antigliadin antibodies (AGA) with xylose absorption test in diagnosis and follow-up of pediatric celiac disease. Three groups of children were investigated: celiacs, affected by other gastrointestinal disease, healthy controls. On gluten diet AGA IgA, IgG and xylose test were abnormal in all celiac children. After only three months of gluten-free diet, abnormal AGA IgA values were found in 3%, AGA IgG in 63%, xylose test in 28% of children. Normal values for AGA IgA and IgG and for xylose test were found between 7 and 20 months. On challenge, after 1-4 months of gluten diet, abnormal AGA IgA and IgG values were found in 90% of cases, xylose test only in 27%. As far as the children with other gastrointestinal disease are concerned, 2% had abnormal values for AGA IgA, 22% for AGA IgG and 42% for xylose test. All healthy children had normal AGA IgA, IgG values and xylose test. Our date show AGA IgA the most specific laboratory test, among these investigated, for diagnosis and follow-up of celiac disease.