WCA July 2013

Traditional fibre cables allow the fibre to slide back in the jacket enough for connectors to be attached, sometimes as much as two millimetres. Thus, connectors were designed with backshells that can account for the lack of additional empty space in the cores. These connectors still conform to GRS 326 performance levels or higher. 5 Thermal balancing Finally, since the tape and jacket are bonded together around the glass, thermal performance balancing was required to enable the entire cable to perform under standard thermal conditions. Each material – glass, tape and jacket – has a different level of thermal coefficient of linear expansion. This means that each material within the cable will expand or contract at different rates under different temperature conditions. For example, plastics typically expand and contract up to two orders of magnitude more than glass. In designing this new fibre, Aramid yarn was known to have a negative coefficient of linear expansion. But bonding everything together, most of the effects of thermal coefficients of linear expansion were virtually neutralised. In the end, the cable behaves very similar to the actual glass in terms of expansion and contraction, performing from -40 degrees Celsius to 70 degrees Celsius with minimal attenuation changes. Conventional plenum rated cables typically perform from 0 degrees Celsius to 50 degrees Celsius – as required by plenum cable standards. 6 Conclusions As optical fibre solutions evolve to areas where copper once ruled, the importance of having the same handling, installation and management characteristics as copper wire cannot be underestimated. Optical cables need to have enough strength to be pulled, twisted and cornered similar to copper without affecting performance. By designing new cables that eliminate air and space inside the cable, smaller footprints can be achieved. Replacing the loose Aramid yarns with tape wraps and bonding the cable elements together is enabling a new evolution in small form factor optical micro-cables. This, in turn, will expand the available system solutions to a broader section of customers, while providing optimal density, flexibility and performance of fibre in enterprise applications. 7 Acknowledgments The author would like to acknowledge the help of Ken Nardone, Henry Rice, Bill Jacobsen and Aly Fahd in obtaining data and test information for this paper. This paper was presented at the IWCS symposium November 2012.

Minimum normal grip to lift 5lb

1.2mm optical ‘wire’ after release of pulling tension. Note: No deformation

1.2mm optical ‘wire’

❍ ❍ Figure 4 : Experimental fixture to simulate 5lb (2.25kg) hand pull on 1.2mm patch cord

5lb (2.25kg) load

24-fibre bundle, 1.2 diameter cable

24-fibre bundle, 2.0 diameter cable

By enabling the tape and jacket to bond as a single entity, the fibre cable could be handled much like a piece of copper wire in terms of strength. While many micro-cables are available today, they typically use Aramid yarns intertwined around the fibre. None have actually coupled the yarns, jacket and fibre together. This cable is unique because it uses an Aramid tape instead of loose yarns. The tape can also be stripped using conventional copper cable stripping machines or copper wire stripping machines. Lineman’s scissors can even be used to strip these cables – the first time this has been achievable with a coated fibre without requiring a specialised tool. It should also be noted that RBR fibre, rapidly becoming the standard in FTTX solutions and central offices/ data centres, also adds to the handling qualities of these new fibres. Smaller cables can be bent around tighter configurations to fit various types of modules and installations. 4 Connectorisation The bonding of the tape and jacket, however, created a new challenge with connectorisation. Bonding the two together eliminated the space required for the fibre to “push back” from the connector. Therefore, connectors had to be re-designed specifically for use with these new fibres. These new connectors take into account that the fibre has no push back, or compression capability, within the jacket. ❍ ❍ Figure 5 : Size comparison of 1.2mm and 2.0mm bundled cable

TE Connectivity, 441 Water Street, North Bennington, Vermont, USA

Te l: +1 802 442 5411 Email : info@te.com Website : www.te.com

55

www.read-wca.com

Wire & Cable ASIA – September/October 2007 Wir & Cable ASIA – July/August 13