PhD Alumni

Gatto Alberto

Present position: Temporary research assistant

Thesis title:  Orbital angular momentum division multiplexing in optical communication systems
Advisor:  Pierpaolo Boffi
Research area:  Communications
Thesis abstract:  
This doctoral dissertation concerns the study, design and experimental characterization of an optical system based on orbital angular momentum division multiplexing. The aim of the work is the realization of a complete innovative multiplexing system based on the phase properties of light beams carrying orbital angular momentum, usually named 'optical vortices'. These particular electric fields are characterized by the presence of an exponential phase term that gives a helicoidal profile to the phase structure.

In telecommunications, different ways of multiplexing signals together for increasing the overall capacity of the communication systems are widely used. Commonly employed methods in optical communications are the wavelength division multiplexing and the polarization division multiplexing. In the latter method two orthogonal states of spin angular momentum (i.e. polarization) of the light are multiplexed, in order to double the system capacity. In principle, also the orthogonal states of orbital angular momentum, which are identified by the integer values of l and hence are unlimited, can be multiplexed for increasing the capacity of the communication system.

The orbital component of the angular momentum of light has captured the interest of scientists only in the last two decades: this property of the electromagnetic waves is so still not completely comprehended and theoretical and experimental studies are presently performed. Its exploitation as a 'label' of different propagating channels has been hypothesized for free-space systems, although none has ever realized a real operating system. Moreover, an orbital angular momentum division multiplexing in optical fibers has never been considered until now. In this work, a complete orbital angular momentum division multiplexing system is realized in free space and in fiber-optic propagation space. The exploitation of the orbital angular momentum as a 'dimension' of multiplexing in advanced optical networks can lead to a breakthrough in optical communication systems.