Ernesto Ciaramella

3.4 Gbit/s visible optical wireless transmission based on RGB LED.

In this paper, we experimentally realized a gigabit-class indoor visible light communication system using commercially available RGB White LED and exploiting an optimized DMT modulation. We achieved data rate of 1.5 Gbit/s with single channel and 3.4 Gbit/s by implementing WDM transmission at standard illumination levels. In both experiments, the resulting bit error ratios were below the FEC limit. To the best of our knowledge, these values are the highest ever achieved in VLC systems.

1-Gb/s Transmission Over a Phosphorescent White LED by Using Rate-Adaptive Discrete Multitone Modulation

Light-emitting diodes (LEDs), which will be increasingly used in lighting technology, will also allow for distribution of broadband optical wireless signals. Visible-light communication (VLC) using white LEDs offers several advantages over the RF-based wireless systems, i.e., license-free spectrum, low power consumption, and higher privacy. Mostly, optical wireless can provide much higher data rates. In this paper, we demonstrate a VLC system based on a white LED for indoor broadband wireless access. After investigating the nonlinear effects of the LED and the power amplifier, a data rate of 1 Gb/s has been achieved at the standard illuminance level, by using an optimized discrete multitone modulation technique and adaptive bit- and power-loading algorithms. The bit-error ratio of the received data was

Multiple wavelength conversion for WDM multicasting by FWM in an SOA

1.5\cdot 10^{-3}

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

, which is within the limit of common forward error correction (FEC) coding. These results twice the highest capacity that had been previously obtained.

All-optical signal reshaping via four-wave mixing in optical fibers

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.

All-optical signal reshaping by means of four-wave mixing in optical fibers

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

A new scheme for all-optical signal reshaping is proposed and demonstrated. The strongly depleted mixing between a CW pump and a noisy nonreturn-to-zero (NRZ) signal in a common fiber can provide wavelength-converted signals exhibiting excellent intensity-noise cancellation. Numerical simulations confirm almost complete suppression of intensity fluctuations, simultaneously occurring at several different wavelengths.

Introducing wavelength granularity to reduce the complexity of optical cross connects

It is experimentally demonstrated that the four-wave mixing (FWM) effect in an optical fiber can be exploited to achieve all-optical reshaping. The injection of a signal and a strong continuous-wave (CW) pump into a common dispersion-shifted fiber results in several wavelength-converted replicas of the signal. These spectral components exhibit various reshaping behaviors. Selecting low-order FWM waves, we observe a sinusoidal-like transfer function. However, unlike other reshaping devices, a step-like transfer function is obtained for higher order mixing products. A significant noise compression is observed at the converted output, starting from an input noisy nonreturn-to-zero (NRZ) signal stream.

Cross-Gain Compression in Semiconductor Optical Amplifiers

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.

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

In future transport networks, optical cross connects (OXCs) could optically route wavelength-division-multiplexed (WDM) signals. In order to switch a large amount of channels, OXCs should have much more complex structures, in terms of both optical components and internal controls. To cope with this, we propose to introduce optical granularity: if WDM signals with the same source-destination pair were assigned a group of adjacent wavelengths, they could be optically routed by OXCs as a single channel. This modifies usual routing and wavelength assignment, but reduces the number of optical components in OXCs and also makes it easier to configure and modify connections. Advantages are similar to those that might come from increasing electrical granularity (i.e., using fewer signals with a higher bit rate), if this option were not limited by transmission impairments.