ANALYSIS & OPINION:FIBRE AND CABLE Figure 2: central tube ribbon cable with 144 fibres


A HYBRID CABLE IS A MATURE TECHNOLOGY AND HAS BEEN DEPLOYED IN MANY LONG-HAUL NETWORKS AROUND THE WORLD OVER THE LAST SEVERAL YEARS


25 to 50 per cent of ultra-low-loss fibre (either G.652 or G.654.E) and 50 to 75 per cent of regular G.652.D fibre. In principle, we do not have to limit ourselves to having just two fibre types in a cable and could stretch to three (Table 1). For example, a good combination could be 25 per cent of ultra-low-loss G.652 fibre, 25 per cent of ultra-low-loss G.654.E fibre, and 50 per cent of regular G.652.D fibre. Te reasons for potentially opting for this


configuration are nuanced, yet important. Ultra-low-loss G.654.E fibre typically provides beter performance than ultra-low-loss G.652 fibre, but G.652 maintains O-band (1310nm) compliance. So, the split between the three fibre types in a hybrid cable could partially be determined by O-band compliance vs C-band transmission performance considerations.


Cable designs Te cable itself can be based on loose-tube or ribbon design, both of which can effortlessly support multiple fibre types. Identifying and splicing the correct fibres is critical in any optical cable deployment, but it is arguably of even greater importance when dealing with multiple fibre types. Loose tube and ribbon cables both have design features that enable simple fibre identification, so the choice between the two then depends on handling preferences and the speed with which the cable must be installed.


Loose tube cables Figure 1 shows a loose tube cable which is the most widely-deployed outdoor cable design. Available with up to 864 fibres, this cable type typically features groups of 12 or 24 coloured optical fibres loosely contained within coloured buffer tubes which are stranded around a central strength member, all contained within a black polyethylene (PE) jacket. Not only does this construction allow


stringent fibre management, it also enables the use of different fibre types in different buffer tubes. Each of the fibre tubes can be identified


quickly and easily by their simple color-coding, meaning there should be no concerns about a technician confusing fibre types during routine installation and maintenance.


www.fibre-systems.com @fibresystemsmag Issue 26 n Winter 2020 n FiBRE SYSTEMS 31


Ribbon cables Figure 2 shows a central tube ribbon cable. Tis cable design is also based upon groups of 12 coloured optical fibres, but these are encapsulated in an array (also known as a ribbon) which are then stacked to achieve fibre counts up to 864 fibres. Te ribbon stack is contained within a single, central buffer tube and the cable is finished with strength members and a black PE jacket. Te ribbon itself is printed with unique


identification information meaning that again, an installer will be able to easily differentiate between different fibre types. Te key benefit of ribbon cables is that


they enable mass-fusion splicing, whereby two 12-fibre ribbons can be fused in a single procedure which makes splicing a full cable up to 80 per cent faster than splicing fibres individually in a loose tube cable with an equivalent fibre count (see Table 2).


Making decisions on the types of fibre in


the face of technological uncertainty that has historically surrounded the field can be difficult. Traditionally, network operators had to


make tough decisions on whether to deploy Fibre X or Fibre Y, but fortunately in today’s environment a hybrid cable consisting of two or three fibre types can represent an effective solution. A hybrid cable is a mature technology and


has been deployed in many long-haul networks around the world over the last several years, and we expect it will become a de-facto choice in the foreseeable future. n


Mathew Guinan is market and technology development manager and Sergei Makovejs is high-data-rate optical fibre market and technology development manager at Corning Optical Communications


Table 1: an example of hybrid cable consisting of three fibre types and associated benefits Table 2: direct comparison: loose tube and ribbon cables


ANALYSIS & OPINION:INSTALLATION


Corning


Corning


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