Photonically-synthesized Digital-to-Analogue Conversion

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Digital-to-Analogue Conversion (DAC) that links the digital domain of '1s' and '0s' to the real-world analogue signals (current and voltage) is an indispensable functionality that enabled the modern ICT. High-speed and high-resolution of DAC, which can generate arbitrary RF signals, is the basis of various applications spanning optical communications, mobile communications, high-definition imaging and the emerging virtual reality. Nevertheless, the realisation of high-speed and high-resolution DAC is extremely challenging due to two reasons. First, there is a trade-off between the resolution (measured by the signal to noise and distortion ratio) and the speed of the DAC. Second, the conventional method of improving DAC speed by reducing the transistor size is now approaching the fundamental limit of electronic fabrication, in which the smallest transistor only contains 10s of atoms. On the other hand, photonics offer over 1000 times more bandwidth resource than conventional radio frequency (RF) electronic device. The substantial technological progress of optoelectronic component in the last decade has enabled a fine control of the amplitude and phase of a lightwave. Photodiode that converts the optical signal to electrical current now can achieve more than 100 Gigahertz frequency range. This project aims to unlock the potential of photonics technologies for future high-speed, high-resolution photonically-synthesized DAC (PhotoDAC) that is capable of generating arbitrary RF signals beyond the bounds of electronic fabrication. This capability will be enabled by a joint innovation of photonics, electronics, and digital signal processing techniques. In this project, the research team will build a prototype DAC instrument using off-the-shelf and customised components. Control software and digital signal processing schemes will be developed to ensure a durable and high-performance DAC prototype. Based on the prototype DAC instrument, the research team will investigate its application in high-speed optical communications, aiming a significantly increased transmission data rate.