Periodic Reporting for period 4 - LightPipe (Antiresonant Hollow Optical Fibres for a Quantum Leap in Data and Optical Power Transmission)
Periodo di rendicontazione: 2021-01-01 al 2022-06-30
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.
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.
When the LightPipe proposal was written, the technology of Nested Antiresonant Nodeless Fibres (NANFs) did not exist. The whole proposal was based on a large body of numerical work. Many challenges lied ahead regarding the fabrication of such structures.
One of the main successes of Lightpipe has been the demonstration of a reproducible fabrication process to produce NANFs of excellent structural quality and unprecedented optical performance.
The project has achieved numerous world-records and ground-breaking demonstrations of the capability of the technology. In 2018 our first NANF broke the previous world record for the lowest loss in a hollow core fibre, obtained 14 years before with a different technology, Photonic Bandgap Fibre (PBGF). The fibre we disclosed had a minimum attenuation of 1.3 dB/km (previous record: 1.7dB/km) had a bandwidth well in excess of 100nm (vs 20nm), it did not suffer from the surface modes plaguing PBGF, and it had an effectively single mode (vs a few-moded) behaviour. This broke the two-decade long view that PBGF technology represented the only way to achieve low loss in a hollow core fibre.
In subsequent years, we have progressively reduced this minimum attenuation to 0.65 dB/km, 0.28 dB/km, 0.22 dB/km up to the recent 0.174 dB/km, comparable to the loss of glass-guiding fibres.
LightPipe has also demonstrated through data transmission experiments with recirculating loops that NANFs can transmit data through several thousand of kilometres, improving by over 50 times the maximum transmission previously achieved with the state-of-the-art PBGF.
All of these results were centred at the wavelength of interest for long haul optical communications, 1550nm. In addition, we have also shown that at shorter (and longer) wavelengths NANFs can also fundamentally outperform conventional fibres, with loss of only 0.3 dB/km at 1060nm (vs 0.7 dB/km of solid core) and 0.5 dB/km at 850nm (vs 2.2 dB/km).
The project has also discovered unexpected properties of the fibres, like their ultra-low backscattering coefficient and their capability to transmit polarisations with order of magnitude better purity than possible with glass-guiding fibres.
Besides, LightPipe has collaborated with tens of academic and industrial partners to demonstrate applications of NANF technology in fields as diverse as laser assisted rock drilling, quantum key distribution, ultraprecise time and frequency distribution, quantum computing, gas sensing, inertial navigation and laser-based industrial manufacturing.
Many of these results have been disseminated at postdeadline sessions at OFC and ECOC and in high impact journals, including several in the Nature family. Tens of press releases and articles in non-specialist magazines have disseminated results to non-specialist audiences.
Finally, the technology has been successfully transferred to a spin-off company, Lumenisity, that currently produces NANFs (and cables containing these) in volume. As a result of the success in this ERC project and of NANF technology, Lumenisity has now created nearly one hundred new jobs in a thriving and fast expanding new sector, with a significant return for the local economy and for the global fibre optics industry.
One of the main successes of Lightpipe has been the demonstration of a reproducible fabrication process to produce NANFs of excellent structural quality and unprecedented optical performance.
The project has achieved numerous world-records and ground-breaking demonstrations of the capability of the technology. In 2018 our first NANF broke the previous world record for the lowest loss in a hollow core fibre, obtained 14 years before with a different technology, Photonic Bandgap Fibre (PBGF). The fibre we disclosed had a minimum attenuation of 1.3 dB/km (previous record: 1.7dB/km) had a bandwidth well in excess of 100nm (vs 20nm), it did not suffer from the surface modes plaguing PBGF, and it had an effectively single mode (vs a few-moded) behaviour. This broke the two-decade long view that PBGF technology represented the only way to achieve low loss in a hollow core fibre.
In subsequent years, we have progressively reduced this minimum attenuation to 0.65 dB/km, 0.28 dB/km, 0.22 dB/km up to the recent 0.174 dB/km, comparable to the loss of glass-guiding fibres.
LightPipe has also demonstrated through data transmission experiments with recirculating loops that NANFs can transmit data through several thousand of kilometres, improving by over 50 times the maximum transmission previously achieved with the state-of-the-art PBGF.
All of these results were centred at the wavelength of interest for long haul optical communications, 1550nm. In addition, we have also shown that at shorter (and longer) wavelengths NANFs can also fundamentally outperform conventional fibres, with loss of only 0.3 dB/km at 1060nm (vs 0.7 dB/km of solid core) and 0.5 dB/km at 850nm (vs 2.2 dB/km).
The project has also discovered unexpected properties of the fibres, like their ultra-low backscattering coefficient and their capability to transmit polarisations with order of magnitude better purity than possible with glass-guiding fibres.
Besides, LightPipe has collaborated with tens of academic and industrial partners to demonstrate applications of NANF technology in fields as diverse as laser assisted rock drilling, quantum key distribution, ultraprecise time and frequency distribution, quantum computing, gas sensing, inertial navigation and laser-based industrial manufacturing.
Many of these results have been disseminated at postdeadline sessions at OFC and ECOC and in high impact journals, including several in the Nature family. Tens of press releases and articles in non-specialist magazines have disseminated results to non-specialist audiences.
Finally, the technology has been successfully transferred to a spin-off company, Lumenisity, that currently produces NANFs (and cables containing these) in volume. As a result of the success in this ERC project and of NANF technology, Lumenisity has now created nearly one hundred new jobs in a thriving and fast expanding new sector, with a significant return for the local economy and for the global fibre optics industry.
Some of the main results achieved during this ERC are:
1) Reduction of hollow core fibre (HCF) loss to values comparable to/lower than those of standard telecoms fibres. The lowest loss officially reported was 0.174 dB/km, an improvement of ~10 times over the state-of-the-art before the start of the project.
2) Demonstration that high-capacity data signals can be transmitted through several thousand of kilometres of NANF. This improves the pre-LightPipe long-distance data transmission record in a HCF by ~50 times and shows that these fibres can potentially ultimately support long-haul and even submarine transoceanic transmissions.
3) Demonstration that HCF of NANF design can offer fundamentally lower propagation loss than conventional silica-based fibres at commercially relevant wavelengths of 850, 1060 and 1300nm.
4) First demonstration that propagation inside HCFs can offer polarization purities order of magnitude higher than solid core fibres, without the need of a large birefringence. For interferometric sensors relying on the propagation of extremely pure states of polarisation, this can be revolutionary.
5) First demonstration of the exceptional capability of NANFs to transmit high average power (kW CW scale) over long distances (km to tens of km ultimately). The experiment conducted within the project achieved by far the highest laser power times distance ever achieved in an optical fibre.
1) Reduction of hollow core fibre (HCF) loss to values comparable to/lower than those of standard telecoms fibres. The lowest loss officially reported was 0.174 dB/km, an improvement of ~10 times over the state-of-the-art before the start of the project.
2) Demonstration that high-capacity data signals can be transmitted through several thousand of kilometres of NANF. This improves the pre-LightPipe long-distance data transmission record in a HCF by ~50 times and shows that these fibres can potentially ultimately support long-haul and even submarine transoceanic transmissions.
3) Demonstration that HCF of NANF design can offer fundamentally lower propagation loss than conventional silica-based fibres at commercially relevant wavelengths of 850, 1060 and 1300nm.
4) First demonstration that propagation inside HCFs can offer polarization purities order of magnitude higher than solid core fibres, without the need of a large birefringence. For interferometric sensors relying on the propagation of extremely pure states of polarisation, this can be revolutionary.
5) First demonstration of the exceptional capability of NANFs to transmit high average power (kW CW scale) over long distances (km to tens of km ultimately). The experiment conducted within the project achieved by far the highest laser power times distance ever achieved in an optical fibre.