ORC led fibre research shows promise for ultra-stable applications

A team from the Optoelectronics Research Centre, home to the Photonics Hyperhighway Programme, has published their research into the development of an advanced fibre with zero-sensitivity to temperature changes.

Published in Nature's group Scientific Reports journal, the paper entitled; "Ultralow thermal sensitivity of phase and propagation delay in hollow core optical fibres", reveals key developments in optical signal propagation time and frequency characteristics.

The research has been conducted by a team from the ORC's Coherent Optical Signals and from the Microstructured Fibre groups, in collaboration with the Time and Frequency Group at the National Physical Laboratory in Teddington, UK. It explores the development of a robust hollow core fibre suitable for use in demanding applications, such as the distribution of accurate time signals, that are very sensitive to environmental variation, for example to changes in temperature.

Dr Radan Slavik, Principal Investigator for the project and leader of the Coherent Optical Signals group, says: “This represents a new and quite exciting research direction for my team. Optical fibre is a great medium for guiding light, but there are still aspects of its performance that are far from ideal with current fibre technology. One of them is its large temperature sensitivity – addressing this issue opens up a whole range of scientifically interesting and industrially relevant applications, and I am currently applying for further funding to research these”.

Propagation time through an optical fibre changes with the environmental conditions occurring where the fibre is laid, since changes in the temperature alter both the fibre length (by a tiny but still significant fraction) and the refractive index associated with the silica glass at its core. These changes have a negligible impact for most fibre applications such as telecommunications, however, they can be greatly detrimental in many others such as fibre-based interferometric experiments and devices.

The paper shows that hollow core photonic bandgap fibres (HC-PBG) have a significantly smaller sensitivity to temperature variations than traditional solid core fibres. The researchers observed a reduction in thermal sensitivity by a factor of 18, making these fibres the most environmentally insensitive fibre technology available to date.

Radan explains: “These fibres are promising candidates for many next-generation fibre system applications that are sensitive to drifts in optical phase or absolute propagation delay. The combination of their unique properties makes the fibres attractive for a range of applications, including gyroscopes, fibre interferometers and the delivery of precise synchronisation signals.”

Dr Giuseppe Marra from the National Physical Laboratory comments: “Optical fibres are playing an increasingly important role in state-of-the-art frequency metrology: from fibre-based devices in the laboratory to the international comparison of optical clocks between National Metrology Institutes. However, in all these ultra-stable applications, the fibre sensitivity to temperature changes is a major concern. The fibre developed at the ORC is opening a whole range of new possibilities.”

The work was supported by HEFCE’s Higher Education Innovation Funding (HEIF), administered by the University’s Zepler Institute as a competition to stimulate research with the potential to generate larger funding and industrial interest. The ORC team’s research was one of nine successful HEIF projects from across the Institute, each sharing in £100,000.

To read the paper in full visit www.nature.com/articles/srep15447

Find out more about the work of the National Physical Laboratories.