The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion. Until now, the photonics-based generation and detection of radio-frequency signals have been studied separately and have not been tested in a radar system. Here we present the development and the field trial results of a fully photonics-based coherent radar demonstrator carried out within the project PHODIR. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system.

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Scaffardi, M. et al. (2017) A silicon microring optical 2 × 2 switch exploiting orbital angular momentum for interconnection networks up to 20

A 4OAMx4WDM switching experiment has been carried out combining an innovative integrated tunable OAM multiplexer based on 4-concentric omega-shaped silicon waveguides and a refractive element-based OAM demultiplexer; operation is demonstrated up to 120Gb/s.

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We propose and demonstrate a technique for the generation of an optical comb with tunable line spacing in a periodically poled lithium niobate (PPLN) waveguide. The technique is implemented with four input continuous waves (CWs), which generate a 19-line comb tuned to the spacing of 25 and 20 GHz. We show that each additional CW switched on out of the quasi phase-matching band at the PPLN waveguide input generates the growth of six new lines. The performance of the comb is tested modulating the lines with a 40 Gb/s differential quadrature phase shift keying data, demonstrating error-free operation. Nonuniform spacing of the input seed CWs improves the efficiency of the line generation process.