Photonically-synthesized Digital-to-Analogue Conversion

数模转换（DAC）将“1”和“0”的数字域连接到现实世界的模拟信号（电流和电压），是实现现代ICT不可或缺的功能。高速、高分辨率的DAC可以产生任意的射频信号，是光通信、移动通信、高清成像和新兴的虚拟现实等各种应用的基础。然而，由于两个原因，高速高分辨率DAC的实现极具挑战性。首先，在分辨率（由信噪比和失真比测量）和DAC的速度之间存在权衡。其次，通过减小晶体管尺寸来提高DAC速度的传统方法现在已经接近电子制造的基本极限，其中最小的晶体管只包含10个原子。另一方面，光子学提供比传统射频（RF）电子设备多1000倍以上的带宽资源。近十年来，光电子元件的技术进步使光波的振幅和相位的精细控制成为可能。将光信号转换为电流的光电二极管现在可以实现超过100千兆赫的频率范围。该项目旨在为未来高速、高分辨率光子合成DAC （PhotoDAC）释放光子技术的潜力，该技术能够产生超出电子制造界限的任意射频信号。这种能力将通过光子学、电子学和数字信号处理技术的联合创新来实现。在这个项目中，研究团队将使用现成的和定制的组件构建一个DAC仪器的原型。将开发控制软件和数字信号处理方案，以确保持久和高性能的DAC原型。研究小组将以DAC仪器原型为基础，研究其在高速光通信中的应用，以期显著提高传输数据速率。

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.