Fibre optics has revolutionised telecommunications, enabled the widespread diffusion of the internet and profoundly impacted industrial manufacturing. In many applications however, fibres are now being operated very close to fundamental physical limits of the glass that forms their core, and this is provides hard limits, for example, to the maximum data capacity or optical intensity that can be transmitted through them.
Air guiding hollow core fibres can provide a natural solution, but the state-of-the-art technology suffers from physical limitations that bound their minimum loss, maximum information capacity, and transmitted optical power and energy. This proposal addressed these global challenges by developing the ‘ultimate’ hollow core optical fibre technology based on nested antiresonant nodeless fibres (NANFs).
These fibres, whose design was invented by the PI but which had never been fabricated before the start of the project, exploit antiresonances and multiple coherent reflections from the glass membranes to achieve a waveguide that shares many of the advantages of free-space propagation.
Lightpipe has successfully demonstrated that NANFs can be produced on a standard fibre optics draw tower, and that their optical properties match the outstanding theoretical predictions. In the space of a few years, they have become the best-performing form of hollow core fibre, breaking all records for lowest loss and longest data transmission distance. The technology has been ground-breaking in many fields. It has achieved the lowest loss ever demonstrated in an optical fibre at wavelengths of 850, 1060 and 1300nm, of significant interest to datacoms and laser delivery for manufacturing. Its unique properties, stemming from a <0.01% overlap of the optical field with the glass include >1000x lower backscattering coefficient, >1000x better polarisation purity and 20x lower sensitivity to temperature variations than conventional fibres. These open up unprecedented opportunities in many scientific and commercial fields, enabling novel applications such as laser assisted drilling in oil wells, ultraprecise long-distance transfer of timing signals and potentially laser driven particle acceleration. In addition, NANFs developed within LightPipe have demonstrated the potential to compete with solid core versions, and in many regards to ultimately overperform them, in the field of optical communications. The project has demonstrated hollow core NANFs with a loss comparable to that of conventional fibres (0.17 dB/km), the ability to transmit high-capacity data through several thousand of kilometers, and, with further work, the potential to transmit up to five times the data throughput of conventional fibres in revolutionary unamplified spans of several hundred kilometres.
