Researchers at the Optoelectronics Research Centre, Southampton, UK, have successfully manufactured a record 11km of a special type of optical fibre; hollow core photonic bandgap fibre (HC-PBGF), a type of fibre that until now had only been made in lengths limited to hundreds of meters.
The fibre, which supports >200nm bandwidth with a longitudinally uniform loss of approximately 5dB/km at the “telecoms wavelength” of 1560nm, has a 19 cell core and 5 cladding ring structure and was fabricated using a conventional two-stage stack-and-draw technique.
“Hollow core photonic bandgap fibre has only had niche applications up until now because it was thought that it could not be manufactured in lengths suitable for telecoms applications,” said Dr Marco Petrovich, a senior member of the ORC team developing hollow core fibre technology with funding from both the UK Engineering and Physical Sciences Research Council and European Union FP7 programme.
Petrovich and his colleagues have demonstrated that the fibre has error-free, low-latency, direct-detection 10Gbit/s transmission across the entire C-Band: the band used for satellite and long distance telecommunications.
Manufacturing long lengths of photonic band gap fibre is notoriously difficult because unlike conventional fibres, whose properties depend on the materials used to make them, the properties of photonic bandgap fibres depend on their structure. The nodes and struts that give photonic bandgap fibre its properties are usually on a sub-micron scale with many even just a few nanometers in size.
The breakthrough was enabled due to an improved understanding of fibre properties deriving from various new numerical and experimental fabrication and characterisation tools recently developed by the team of researchers.
“We demonstrated data transmission at 10Gb/s along a 11km span using direct detection, showing only minor penalties and achieving an estimated >15?s latency reduction relative to standard fibre,” said Petrovich. “Our numerical models of the fibre drawing process give us confidence that much longer fibre yields are feasible through further scaling of the process, and that much lower loss fibres should ultimately be possible.”
By Matthew Peach