ANDY EXTANCE OPTICAL FIBRE
“In the future more integrated fibres, transponders, amplifiers and multiplexers will become necessary throughout optical communications.”
G.652.D fibre core area,” Lingle explained.
ULTRA LOW LOSS Consequently OFS has developed ultra-low loss fibre for terrestrial optical communication, with the maximum 125µm2 practical e ective area, called TeraWave ULL. “OFS took a family of fibre designs and a manufacturing platform developed for the submarine market and optimised it for terrestrial cabling and practical Raman amplification,” Lingle explained. “The result is a fibre that helps extend the un-regenerated reach for 200Gb/s coherent links beyond 4500km.” Meanwhile, 5G wireless networks will need more front-haul and back-haul fibre cable, to support a higher density of cells, Lingle added. OFS’ bend-insensitive AllWave FLEX and AllWave FLEX Max fibres will optimise cable performance between macro-cells and small cells, he said. Vodafone is working with vendor partners to improve spectral e ciency using existing fibre assets, Rossi revealed. “In addition we are looking to increase the spectral e ciency of the fibre using flexible spectrum operations managed using software defined networks,” she said. “The advantages of large e ective area fibres would be mostly in the long distance applications where we typically use dark fibre at present.” However, dark fibre providers are already running short of long-haul assets, Lingle said. “Much dark fibre remaining is older G.655 fibre, which is less optimised for advanced coherent modulation formats,” he said. “As a result, there is a resurgence in the long haul cable market, driven by cloud companies.” TeraWave ULL fibre has therefore already been selected for deployment by several cloud content providers, Lingle added. The demand for innovative fibre technologies to boost spectral e ciency is already here, it seems – and, for now at least, suppliers continue to have the ingenuity to satisfy it.
Peter Winzer– Nokia Bell
core fibres. “Applicability will depend on the volume of production and its competitive commercial availability,” she said. She also echoes Winzer’s words on how they have to fit in to existing operations, in particular in operating reliably. “Vodafone’s focus is on delivering gigabit services to end users,” she said. “Anything that impacts the ease of installing and maintaining fibre lines e ciently on behalf of our customers will a ect us.” However, pushing spectral e ciency higher than is currently possible with 100Gb/s QPSK modulation coherent technology requires other options for moving beyond established G.652.D specification fibre designs, Lingle stressed. Long distance connections between cloud datacentres in particular need to implement higher order modulation formats like 8QAM and 16QAM. “These formats require higher optical signal-to-noise-ratio and are more sensitive to non-linear impairments from the 80µm2
gradually transition from a WDM to a WDMxSDM infrastructure.” NEW DESIGNS Recently Norcross, Georgia- headquartered OFS and its parent company Furukawa Electric, in Tokyo, Japan, have developed multi-core, few-mode, and hollow-core fibres that might suit SDM. Robert Lingle, OFS’ Director of Market and Technology Strategy, warns that hollow- core fibres have significantly higher loss than standard fibres and are di cult to fabricate. However, they reduce the transit time of signals by around 30%. “They may become practical in the near future for applications where lower latency is of very high financial benefit,” Lingle underlined. Similarly multi-core fibres “probably await a breakthrough in the cost of manufacturing” before widespread use in optical communications. Rossi emphasised that Vodafone is tracking ‘new developments in the field’ like multicore and hollow-
to a di erent wavelength necessitates a complete technology change,” he says. Fundamentally reducing
the cost per bit using SDM technologies will be a challenge, Winzer admitted. “The key is a
smooth upgradability path that re-uses deployed fibre infrastructure,” he asserted. “Bell Labs is working on exactly these kinds of evolutionary systems that allow our customers to
Space division multiplexing squeezes more data into fibre by sending light down di erent paths. NOKIA BELL LABS
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ISSUE 9 | Q2 2017
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