Orbital angular momentum and beyond in free-space optical communications

Orbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting, N-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.

Machine Learning Applications for Short Reach Optical Communication

With the rapid development of optical communication systems, more advanced techniques conventionally used in long-haul transmissions have gradually entered systems covering shorter distances below 100 km, where higher-speed connections are required in various applications, such as the optical access networks, inter- and intra-data center interconnects, mobile fronthaul, and in-building and indoor communications. One of the techniques that has attracted intensive interests in short-reach optical communications is machine learning (ML). Due to its robust problem-solving, decision-making, and pattern recognition capabilities, ML techniques have become an essential solution for many challenging aspects. In particular, taking advantage of their high accuracy, adaptability, and implementation efficiency, ML has been widely studied in short-reach optical communications for optical performance monitoring (OPM), modulation format identification (MFI), signal processing and in-building/indoor optical wireless communications. Compared with long-reach communications, the ML techniques used in short-reach communications have more stringent complexity and cost requirements, and also need to be more sensitive. In this paper, a comprehensive review of various ML methods and their applications in short-reach optical communications are presented and discussed, focusing on existing and potential advantages, limitations and prospective trends.

PR39_FellowshipResearchReport

Summary of a Project Outcomes report of research funded by a PhD Fellowship Award from IBM, in the area of integrated photonics and quantum optical communications.

PR_32 Managing Spectral Content in Optical Networks Using Silicon Photonics (1525090-Y3)

We design of compact head-end components at the transceiver level using silicon photonics to implement disaggregation for improving optical communications. We study how to use optical side channels to pass control messages without increasing the number of fibers or input/output ports. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1525090 (Year 3).

PR_31 Back-to-Back Test of Reconfigurable Add-Drop Using a Silicon Photonics Microchip (1525090-Y2)

We study the design of compact head-end components at the transceiver level using silicon photonics to implement disaggregation for improving optical communications, and demonstrate novel functionality at the link level. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1525090 (Year 2).

PR38 Progress Towards Integrated Photon-Pair Sources and Their Applications (1640968-Y5)

The objective of this project was to make significant advances in quantum optical communications through the design, fabrication and demonstration of novel devices at the microchip scale. The principal goal of the device sub-project was to develop key building blocks for photonic microchips that are energy-efficient, leverages modern micro-fabrication platforms, reduces operational complexity and improve scalability with the potential for future adoption by industry. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1640968 (Year 5).

Material strategies for function enhancement in plasmonic architectures

Plasmonic materials are promising for applications in enhanced sensing, energy, and advanced optical communications.

Design and Control Recipes for Complex Photonic Integrated Circuits

In the last decades optical communications contributed to the huge diffusion of the telecommunication market, pushing the development of new technologies to enable higher performances and lower costs.