ANALYSIS & OPINION:FIBRE AND CABLE
MIXING IT UP
A look at building future-ready terrestrial networks with hybrid optical fibre cables
SERGEI MAKOVEJS AND MATTHEW GUINAN A
s demand for bandwidth continues to grow and the applications driving it evolve, network operators face the difficult task of preparing their
physical optical infrastructure for a future that cannot always be envisaged. Te precedents in which new technologies
fundamentally change the way the optical networks are built have happened before, with the most recent and vivid example being the transition to coherent systems in late 2000s – this shiſted the focus away from managing chromatic dispersion to managing noise and nonlinearity. Given that the memories of such a disruptive
technological change are still fresh and that at least another disruption over the lifetime of the cable is almost inevitable, operators are naturally on the lookout for futureproof solutions. Te aim is to make the right decision on passive infrastructure deployment in the presence of incomplete information on future transmission technologies and future network architectures. One way to address this challenge is to deploy hybrid cables to account for potential disruptions that next-generation transmission technologies may bring.
What is a hybrid cable? Simply put, a hybrid optical fibre cable is one that features two or more different fibre types in the same physical construction to provide greater flexibility for the network operator. Each of the fibre types can also serve its own purpose. For example, ITU-T recommends G.652.D compliant fibre (which can be simultaneously compatible with G.657.
30 FiBRE SYSTEMS n Issue 26 n Winter 2020
www.fibre-systems.com @fibresystemsmag
A1) to support direct connections to business customers in a metropolitan network. Conversely, ultra-low-loss G.652 fibre or G.654.E fibre can be used to carry aggregated traffic over longer routes. Te benefits of such ultra-low-loss fibres is their ability to provide higher transmission capacity, longer amplifier spacing, beter transmission margin, stronger repair resilience, or a combination of all of the above. Another, and perhaps frequently overlooked benefit, is the ability to accommodate more reconfigurable optical add-drop multiplexers (ROADMs) in transparent network architectures. It is likely that such networks will become
mainstream in the next 10 years, therefore the decision made today on the fibre plant could reverberate for the next decade and beyond.
Figure 1: loose tube cable with 144 fibres
Deploying optical cables containing hybrid fibre types can give peace of mind that passive infrastructure will be able to cope with what the future throws at it.
Ask yourself this A natural question to ask is what should be the split between a traditional G.652.D fibre and ultra-low-loss G.652 / G.654.E fibre? It really depends on the amount of data traffic that is provisioned for the long-haul part of the network, versus the amount of data traffic that is expected to stay in a metropolitan area. Additional requirements for route protection and redundancy may also play a role. In other words, the desired split ratio will vary from region to region, and from network to network. But a good rule of thumb could be to provision
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