Blog

When he was at university, Dr Zhixin Liu, professor of optical signal processing and communications at University College London (UCL), had his first taste of entrepreneurship. The problem was that it was with someone else’s IP and technology, and the project did not take off. Nevertheless, the seed was planted. “I told myself I want to bring my own invention to a product, to something that can benefit the world, that other people can use,” he explains.

Today, Liu combines his academic career with the role of CTO at Nibras Communications. Nibras aims to develop ultra-low-noise photonic signal sources for satellite and 6G communication systems. “We’re developing signal generators for high frequency,” explains Liu. “The requirement comes directly from the telecom and satellite communities as they are moving to higher and higher frequency.”

The capacity required for satellites to base stations is understandably much greater than that for a smartphone. “The base station needs to handle lots of data – and the only way to create more capacity is to go to higher frequency where you have more frequency resource to use,” says Liu. “Coming to our research, we think about how we can provide bandwidth and flexibility to access any frequency.

“Frequency is a scarce resource; once it’s used, it’s gone,” Liu adds.

As the results of EPSRC research projects (ORBITS, PROSPECT, TRANSNET), the four employees of Nibras – all members of the department of electronic and electrical engineering at UCL – along with another colleagues, published several seminal research papers which outline a proposal for a wide range tunable photonic frequency synthesiser with low and non-scaling phase noise. Frequency synthesisers are used in devices ranging from  base stations to phones and satellites and with use cases across communications, sensing, navigation and spectroscopy. The research posits that conventional frequency synthesis leads to ‘noisy, power-hungry architectures’ at high frequencies, and while many photonic approaches achieve low phase noise – the jitter of an oscillator, in other words – they do so with frequency instabilities.

The researchers offer a solution whose architecture is compatible with integrated photonic implementation, which is good news for potential future chip-scale deployment. 

For Liu, it is a natural fit for someone who says he has been ‘fascinated about combating noise’ for his entire career.

“Low noise means you can see things clearer and you can transmit more data and more information,” he explains. “Motivated by this, we went back to the basics and came up with some new concepts of generating flexible frequency; and this time, we use photonics methods rather than using conventional electronics. We validated its performance using an experimental platform.”

Once the performance was validated, industrial partners shown keen interest in the results. “They got very excited and asked us for samples for evaluation.” says Liu. “Now, part of the mission for Nibras is to build and miniaturise the system so that the solution can scale.”

One shot in the arm for Nibras, also in March, was being selected for the latest ChipStart UK cohort as one of the UK’s most promising early-stage companies. The ultimate goal is to commercialise Nibras’ photonic signal generator for future communications. While Liu can draw to a degree on his previous entrepreneurial experience, along with the six patents he holds, the business understanding of ChipStart has been useful to all. He says the programme has exceeded his expectations.

“It’s a real accelerator,” says Liu. “We participate in weekly-based training, and that has been extremely helpful to us. Currently, the whole team is a technical team; we need to understand the business aspect. The training has been extremely helpful to understand the IP strategy, how investment works and how to prepare for fund raising. That’s a real help for us.”

Liu notes that the wind is blowing in a different direction with regard to semiconductor investment – “when I started applying for research grants 10 years ago, silicon was almost considered a forbidden word in proposals”, he says – allied to the UK’s ‘strong legacy’ in photonics. “I think the ChipStart programme and the Silicon Catalyst [has] come at a perfect time,” he says. “We still have legacy of industry and experiences from the old times and lots of strong researchers and talents being cultivated in the country.”

With a communications focus, the emerging 6G opportunity forms part of Liu’s work. His team hit the headlines in late 2024 after creating a trial system that achieved a 938 Gbps transmission data rate – around 5000 times faster than a good 5G connection of the time. The increasing influence of photonic technologies in this space is apparent; as John Oncea put it in an RF Globalnet article featuring developments at the most recent Optical Fiber Communication (OFC) Conference, it signals ‘the dawn of an engineering paradigm where lightwave-based hardware operates not just as a medium for optical signals but as the backbone for radiofrequency systems up to the terahertz range.’

Liu notes that Nibras’ approach is just one photonic technique to connect photonics with microwaves, but says he has ‘high expectation’ of 6G’s success compared to 5G. He sees a convergence of the microwave community with the photonics community – something which is already taking place, but ‘needs to happen more.’

“When we talk to microwave people, sometimes they get fascinated – ‘oh, photonics can do this’ – and then when photonics sees some of the microwave integrated circuits, you say, ‘oh, what you design is what you get.’ This does not always happen in photonic integrated circuits,” says Liu. “So, I foresee convergence of conventional microwave and photonics industries, where photonics will certainly play a big role in 6G.”

At Microelectronics UK, where bringing communities together is one of the core principles of the event, Liu will be involved with Nibras, as well as speaking around photonics for space. “I’ll be coming from more my academic hat, talking about photonics ecosystem, supply chain and the strengths of UK photonics community, as well as the talent cultivation, with a special focus on how this could support the vision of photonics for space applications, such as ground-to-satellite and inter-satellite communications,” he says.

Editor’s note: The views in this article are the personal views of Dr Liu, and do not necessarily represent those of his employers.