TECH FOCUS OPTICAL FIBRES
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interesting, as one of the early applications for hollow-core fibre could be in intra- data centre networks. Since light travels approximately 30 per cent faster in air than it does in glass, latency would be 30 per cent lower. That adds up to milliseconds saved when moving data, which means improved response times and overall performance. The new programme will also explore
the performance limits of hollow-core fibre technology as well as more reliable means of manufacturing the fibres. The sub- micron features of hollow core fibres are particularly challenging to make, though considerable progress has been made. Other work packages will develop new
Commercial products
Among the latest optical fibre products on the market include photonic crystal fibres (PCF) from NKT Photonics. The firm uses its PCF technology to embed as many functions as possible directly into the fibres to ensure systems are simpler, cheaper, and more reliable. Its PCF portfolio spans
from nonlinear fibres optimised for octave-spanning supercontinuum generation, over single mode ytterbium gain fibres for high power lasers and amplifiers, to advanced hollow core fibres guiding the light in air.
NKT Photonics hollow-core photonic bandgap fibres use a micro-structured cladding region with air holes to guide light in a hollow core. The photonic bandgap guiding mechanism is fundamentally different from the traditional total internal reflection guiding principle. This technology provides the basis for high- power delivery without
nonlinear effects or material damage. As more than 98 per cent
of the mode is confined in air, the fibres are also very radiation insensitive, making them suitable for radiation hard environments. Pump combiners for fibre
lasers and fibre amplifiers from Lightel. Lightel’s high-power pump combiners are mainly used to combine the power of several multi-mode lasers and thus obtain delivery and pump fibres with a high output power. At Laser Components, these passive components are available for applications with up to 37 laser sources and total powers of up to 8,000W. With the air-clad technology
developed by the manufacturer, a rate of efficiency of 90 per cent
30 Electro Optics August/September 2019
and higher can be achieved for power coupling. Depending on the application, the combiners are available with different fibres and fibre combinations. Polarisation-maintaining (PM) configurations are also possible. This technology is used
for both fibre lasers and erbium-doped fibre amplifiers (EDFAs). In addition to stability and reliability, high-power transfer efficiency is crucial. Therefore, it is particularly important to adhere to the strict requirements that apply to production.
Custom designs for single- mode and polarisation- maintaining (PM) fibres are also available upon request. The fibres can also be provided with fibre Bragg gratings.
Excelitas’ The KineFlex UV/ HPV fibre optics beam delivery system (355nm, 375nm, 405nm to 640nm) are robust laser beam delivery systems for single wavelengths in high-power 405- 640nm and UV 355nm and 375nm. These fibre delivery systems are designed around pre-focused and integrated optical assemblies. The fibre is automatically mode-matched to the required laser parameters to achieve transmission efficiencies greater than 65 per cent and guaranteed performance up to high-power levels of 500mW in most wavelengths. KineFlex fibre systems can be customised for exacting OEM specifications. Outputs can be configured to produce pure Gaussian profiles with extremely low-wavefront error, as well as engineered spatial profiles and shapes. Single- mode fibre designs are also available for multi-wavelength, broadband transmission (>200nm bandwidth) and ultra- high vacuum compatibility. EO
@electrooptics |
www.electrooptics.com
methods of interconnecting these new optical fibres to more conventional fibre types as well as other optical components such as lasers – essential if the new technology is to be compatible with existing components and cables. Professor David Richardson, programme
Cross sectional photograph of a Nested Antiresonant Nodeless hollow-core Fibre (NANF) showing a mode being guided in the fibre
lead for AirGuide Photonics, and deputy director of the University’s Optoelectronics Research Centre, said: ‘The ORC has been at the forefront of photonics for over 40 years. Our new AirGuide Photonics programme will continue to push the boundaries of what can be achieved with optical fibres and develop a disruptive technology that puts the UK at the forefront of optical technology.’
Soton/ORC
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