The light Orbital Angular Momentum (OAM) is an extremely attractive degree of freedom for communications, as, in principle, it provides an unlimited number of modes for mode division multiplexing (MDM) corresponding to a significant improvement in communication rate. In the last decades, scientific research has focused many studies to the development of tools and strategies for generating, manipulating and detecting OAMs, both in fibers and free space. The fibers typically operate in the C-band of the Near InfraRed (NIR, 1.55μm), while free space communication links are currently moving towards the Mid-InfraRed (MIR, 4μm), corresponding to the atmospheric transparency window with low background noise and low turbulence effect. Both technologies are essential: fibers are flexible and not subject to atmospheric turbulence, while the free space links are fundamental in complex environmental morphologies and satellite communications. Few-mode fibers (FMFs) supporting the transmission of several modes in the telecom band are now commercially available, together with efficient optical mode multiplexers/demultiplexers (MUXs/DEMUXs), while OAM free space links in MIR have never been realized to date.
The goal of this project is to realize a hybrid OAM multiplexed communication link, operating in their optimal wavelength range and connected via a coherent conversion process.
The conversion will be realized by an Intracavity Difference Frequency Generation (IDFG) to transfer coherently OAM modes to MIR spectral regions by preserving the quality of the modes.
In OAM-based fiber communication over long distances, it is mandatory mitigating the crosstalk between the propagating OAM modes. For this purpose, in the present project, we propose to develop a suitable simulation tool to evaluate and reduce the intermodal crosstalk in FMFs, experimentally validating the results obtained in an advanced 9-LP mode FMF, such as that deployed in L’Aquila town.
At present tools for manipulating OAM, as well as for MUX/DEMUX multiple OAM-carrying beams are relatively missing in MIR. In OMyLink project, we will exploit suitably-designed geometric phase optical components to enable OAM generation, manipulation and detection in this range.
A detailed analysis of the link stability in MIR will be performed, including the study and simulation of the link resilience to atmospheric turbulences.
