Development of orbital angular momentum (OAM)-based subsystems for Communication and Sensing

The primary objective of this thesis is to design and develop systems for switching, transmission and sensing applications exploiting the use of orbital angular momentum (OAM) of light. Different designs of OAM-based subsystems are investigated to support short-reach high-data density application e.g. data-centres. OAM multiplexed fibre transmission, OAM-based switching and OAM-based conversion system effectiveness is demonstrated to facilitate the communication and networking in data-centre networks. A novel two-layer architecture exploiting OAM and wavelength as switching and multiplexing domain is presented. The potential of exploiting OAM as additional switch and multiplexing domain is discussed. Different architectures are analysed, and one design is selected for experimental demonstration in communication and networking environment. A detailed characterisation of the building blocks required for the development of two-dimensional OAM-wavelength switch is presented to demonstrate the feasibility of a compact switch solution for interconnection networks. Initial experiments demonstrated the OAM-wavelength switches based on dual-grating and three superimposed grating micro-rings. Later experiments exploited the use of concentric -shaped waveguides acting as OAM multiplexer to demonstrate a tunable OAM-wavelength switch. The experimental validation of a tunable two-dimensional switch exploiting OAM and wavelength is described. The proposed OAM-wavelength switch is aimed at the tunability constraint of the switches based on micro-rings in the initial experiment. The switch performance is experimentally evaluated by realizing a 4 OAM and 4 WDM switch with 4 ports, cascading 4 -shaped waveguides multiplexer and refractive element-based OAM demultiplexer. The switch is tested in different configurations and with different data formats. The switch performance is also evaluated by applying OpenFlow-based SDN control plane and is tested with real-data traffic. In another experiment the switch exploiting 10 OAM and 16 wavelengths is also demonstrated showing its potential in terms of low power consumption, low footprint and fast switching time. Moreover, this switch was later used to demonstrate OAM– wavelength packet switching controlled by a two-step scheduler (TSS) implemented in FPGA. Designs and characterization of OAM conversion schemes for optical cross connects and add/drop functionality is also presented. A novel scheme for tunable OAM conversion is presented exploiting the -shaped waveguide multiplexer and passive OAM demultiplexer. The OAM converter is developed and experimentally validated using real-data traffic. Moreover, OAM fibre multiplexed transmission is also demonstrated exploiting 10OAMand 16 wavelengths over 1km of graded index ring-core fibre (GIRCF) allowing to achieve high transmission capacity (17.92Tb/s) for short-reach datacentre applications. The OAM-based switching and OAM-based multiplexed transmission schemes are tested in field trials exploiting the Ethernet traffic generated by commercial apparatus typically used in data-centre environments. Moreover, transmission of video traffic through the OAM-based switching system is also presented. In addition to the OAM-based implementations for communication, optical sensing experiments are also performed. In order to evaluate the benefits of OAM for sensing application, OAM of light is experimentally exploited to measure the Doppler shift of the rotating target and characterize the transmission of OAM beams through turbid media for OAM-based tomography. Moreover, a lidar system exploiting dual-wavelength for the measurement of the chlorophyll content in food/vegetation monitoring is also presented to exploit in remote sensing.