Photonically-synthesized Digital-to-Analogue Conversion

Lead Research Organisation: University College London
Department Name: Electronic and Electrical Engineering

Abstract

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.

Planned Impact

It is expected that this project will generate impacts in the academic community and create industrial impact with IP and potential products.

*Academic and research community: This project will benefit researchers in both industry and academia working in the field of telecommunications, microwave, and photonics. The PI will target to publish the research results in high-impact journal publications (e.g. Nature Communications, Journal of Lightwave Technology), and top international conferences (e.g., OFC, ECOC, CLEO). The research outcomes from this project will also be disseminated to academic researchers via workshop, press release, and seminars. This project will create a new interdisciplinary research area that innovates DAC using photonics means. It is also expected that the success of this project will lead to a follow-up project focusing on a fully-integrated photoDAC.

*Creation of new products: A successful development of the high-speed high-resolution DAC prototype will result in a new instrument that can be commercialised. In addition to the overall DAC system, this project will develop two key subsystems, the tone extraction subsystem and the coherent synthesis subsystem, both of which have potential to be commercialised in their own right. The PI will explore potential product development through the collaboration with the industrial partners (Eblana and Oclaro). The partners will have access to UCL's state-of-the-art testing facilities, which will undoubtedly promote their product development and innovation. If the demand for the instrument/technology developed in this project is sufficient to generate a steady income, the PI will also consider creating a new spin-off company.

*Educate the future engineers, researchers and innovators: Skill development will be first applied to the involved student and PDRA. The industrial partners will dedicate effort and time to train the student and PDRA involved in this project. The PI is one of the supervisors in the UCL-Cambridge Doctoral Training (CDT) in Integrated Photonic and Electronic Systems. Through the CDT and UCL's undergraduate lectures, the PI will educate and train new researchers and innovators with the necessary skills for this research field.

*Impact beyond ICT: The functionality and subsystems developed within this project are directly transferable to other sectors within and beyond ICT. This project will benefit other non-expert knowledge users who may apply the developed technologies in their fields and products.
 
Description 1. We invent and experimentally prove a new method to amplify a single wavelength light without adding extra noise, based on which we can build our photonic-assisted analogue-to-digital converter;
2. We invent (patented) a new approach to realise conversion between analogue signals (e.g. voltage and current) and digital bits of 1s and 0s. Such approach is the gateway between the realise world and the digital world that we have built. Through our proof-of-concept experiments, we show our new methods have the potential to overcome the fundamental limits of speed (bandwidth) and noise in conventional electronic-only digital-to-analogue converters.
Exploitation Route Patent licencing. Paper publication that other researcher can learn from our findings and our new approaches for their research.
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Other

 
Description Comb tone extraction through optical injection locking of microring lasers 
Organisation Hewlett Packard Enterprise (HPE)
Country United Kingdom 
Sector Private 
PI Contribution We brought the technology of stable optical injection locking and its application in the selection and amplification of individual tones in frequency comb. Through collaboration experiment at HPE site we achieved >20Gb/s data transmission using quantum dot microring lasers. This collaboration has led to two conference papers, two journal submission, and one joint patent application.
Collaborator Contribution The partner, HPE, are the world leading manufacturer of microring lasers, optical interconnect systems and high performance computing systems. This collaboration provided the PI access to the state-of-the-art quantum dot comb lasers and microring lasers, opening new application of injection locking technologies. HPE has made direct contribution to the project by donating research components, and in-kind contribution through visit the PI and contributing to joint research.
Impact D. Liang et al., "Optical injection-locked high-speed heterogeneous quantum-dot microring lasers", ECOC, 2019. D. Liang et al., "Heterogeneous Multi-wavelength Optical Injection Locked System-on-chip: a Proposal & Proof-of-concept Experiment," Asia Communications and Photonics Conference, M4D.4, 2019.
Start Year 2018
 
Description Electronic pre-equalisation of directly modulated lasers 
Organisation Eblana Photonics Ltd
Country Ireland 
Sector Private 
PI Contribution The PI and his team design and optimise pre-emphasis equalisers that improve the signal-to-noise ratio of bandwidth limited directly modulated lasers. We also contribute to this collaboration our digital signal processing expertise, based on which we demonstrated improved performance for 64Gb/s and 128Gb/s direct modulation and direct detection transceivers.
Collaborator Contribution The collaborator provided this collaboration with their research devices (directly modulated discrete mode lasers). Currently the collaborator also incorporated the new designs in their device manufacturing for next stage collaboration.
Impact One joint paper publication. Z. Zhou et al., "Impact of Analog and Digital Pre-emphasis on the Signal-to-Noise Ratio of Bandwidth-limited Optical Transceivers", IEEE Photonics J., DOI:10.1109/JPHOT.2020.2966617, 2020
Start Year 2018
 
Description Gain-switching of injection locked high-speed directly modulated for comb generation 
Organisation II-VI Incorporated
Country United States 
Sector Private 
PI Contribution In 2019, the PI builds a new collaboration with II-VI, which is one of the biggest optical device manufacturers in the world and is leading the research on optical transceivers especially directly modulated lasers. The PI visited their headquarters at Sunnyvale California (locate at the centre of silicon valley) and gave a talk on his research (optical injection locking and application). After that, the PI visited their principle laser scientist Matsui-san at Fremont California and spent a week there doing a joint experiment. The PI brought injection locking technology to the partner which helps demonstrate a gain-switching of directly modulated at a record high repetition rate, generating significant impact in laser science and optical communication fields.
Collaborator Contribution This new collaboration gives PI and the PhotoDAC project access to new laser technologies and received a donation of state-of-art laser device (worth more than £10k) for future work. This new collaboration has also led to an internship programme that allows UCL PhD students to take an internship at II-VI laser labs.
Impact Joint publications in journal and top conference: Z. Liu et al., "50-GHz Repetition Gain Switching Using A Cavity-enhanced DFB Laser Assisted By Optical Injection Locking," J. Lightw. Technol., DOI: 10.1109/JLT.2020.2973198, 2020 Z. Liu et al., "50-GHz Gain Switching and Period Doubling Using an Optical Injection Locked Cavity-enhanced DFB Laser," OFC, T3C.1, 2020
Start Year 2019
 
Title Injection locked multi-wavelength optical source 
Description The patent disclosure describes various examples of optical systems (e.g., optical transceivers) that include an optical transmitter having an injection locked multi-wavelength optical source. According to embodiments as described herein, the injection locked multi-wavelength optical source includes a first optical source configured to emit light having different wavelengths, a waveguide, and an optical coupler configured to couple the emitted light from the first optical source to the waveguide. The injection locked multi-wavelength optical source further includes an array of two or more second optical sources coupled to the waveguide. Each of the two or more second optical sources are configured to be injection locked to a different respective wavelength of the emitted light transmitted via the waveguide from the first optical source. In some implementations, the first optical source is a master comb laser and the two or more second optical sources are slave ring lasers of the injection locked multi-wavelength optical source. 
IP Reference USA or PCT App. No. 16/582907 
Protection Patent application published
Year Protection Granted
Licensed Commercial In Confidence
Impact Patent sold to Hewlett-Packard Enterprise as an IP for their super computing product.
 
Title SIGNAL PROCESSOR APPARATUS 
Description The invention disclose an optical assisted signal processing apparatus that allows for significant increased bandwidth and solution of analog to digital conversion. 
IP Reference UK app. No.: RET103662P.GBA 
Protection Patent application published
Year Protection Granted
Licensed No
Impact Currently we are negotiating with industry company for the further development of the patent.
 
Description Low Latency Clock Recovery for Optically-switched Data Centres 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact participated in workshop during the top conference in computer science (SIGCOMM'19), discuss new concepts and opinion with international colleagues with more than 70 audience.
Year(s) Of Engagement Activity 2019
 
Description OFC Tutorial : optical injection locking and its application in optical transceivers 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact OFC invited tutorial on optical injection locking, with more than 100 professionals attending the presentation.
Year(s) Of Engagement Activity 2019
 
Description UCL all academic festival 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I participated in the UCL all academic festival where I organised laboratory open day and hosted five groups of general public to explain photonics, optical communications and the importance of ICT for everyday lives.
Year(s) Of Engagement Activity 2019
 
Description Using low thermal sensitivity hollow core fibre for optically-switched data centre applications 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact PhD student Kari Clark presented this top scored paper at the prestigious European Conference on Optical Communication (ECOC), Dublin in Sept 2019. Lidia woekshop was attended by 100+ attendees with excellent feedback received.
Year(s) Of Engagement Activity 2019
 
Description Visit and Seminar at Beijing Institute of Technology in China 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact I visited the Advanced Research Institute of Multidisciplinary Science and give a seminar on Low Latency Clock Recovery for Optically-switched Data Centres. The audience contains about 30 postgraduate students and academics.
Year(s) Of Engagement Activity 2019
 
Description Visit and Seminar at Huazhong University of Science and Technology in China 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact The PI visited the fibre device group at National Laboratory of Optoelectronics at the Huazhong University of Science and Technology in China ( http://english.wnlo.hust.edu.cn/), give a seminar on optical injection locking and their applications, with 20+ audience including postgraduate students and academics. I also discussed collaboration with the academics.
Year(s) Of Engagement Activity 2019
 
Description Visit and Seminar at Nanyang Technological University in Singapore 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact I visit the Photonic Institute at Nanyang Technological University in Singapore (http://tpi.ntu.edu.sg/aboutTPI/Pages/Our-People.aspx) and their centre director Prof. Perry Shum at Centre for Optical Fibre Technology (COFT). I give a seminar organised by IEEE photonic chapter in Singapore with about 20 audience (postgraduate students and academics).
Year(s) Of Engagement Activity 2019