Spring 2018 Optical Connections Magazine


Dust-proof: A ruggedized Harting connector.

piece of dirt between a pair of ceramic

connector can initially be cleaned by rinsing it in water and then the inner optic faces dried and simply wiped clean with a cloth or tissue, fully restoring signal transmission operation. Daisy-chain and through bulkhead I/O cable assemblies are supplied with fitted covers, as it is always good practice to minimise the ingress of dirt and dust in any fibre-optic connector where possible, thus further extending its lifetime. The aluminium shell housings and covers have a shock-protected rubber boot, and the interlinking fibre-optic cable includes an inner Kevlar crush- resistant sleeving that provides cushioned protection to the integrated optical fibres. As a result, the daisy-chain cables oer a rugged and robust field installation solution. The distinctive yellow colouring of the HARTING expanded-beam FO cable assemblies enables users to easily identify them as containing fibre-optic components and sets them apart from other copper-based cables. Users can then ensure that they take account of the allowed fibre-optic bend radius characteristics for the installed laid cables. Harting’s expanded-beam fibre-optic connectors and cables described in this article provide outside-broadcast systems integrators with full assurance of their long-term reliability, ensuring continuity of service even under harsh environmental installation and operating conditions.

weight of the installed vehicle. Fibre-optic cables are inherently immune to EMI/ RFI interference and cannot contribute to ground loops. One of the other key benefits of fibre optic systems is their general immunity to interruption by moisture or immersion in water, as there is no electrical current to cause short circuits. However, it is the environmental operational conditions that need to be considered carefully when installing fibre- optic cabling systems in the field. Particular attention has to be paid to the potential for ingress of dust and dirt, especially for multiple mating situations: so much so that butt-jointed fibre-optic connector types are only normally suited for controlled environment conditions, where dirt and dust is minimised and connectors can easily be routinely cleaned. Nevertheless, it is possible to apply fibre optics in much harsher environment operating conditions, such as those experienced in outdoor installations, by utilising expanded-beam fibre-optic connector design technology. EXPANDEDBEAM CONNECTORS In an expanded-beam connector, the diameter of the optical beam is expanded by approximately 40 times, and this expanded beam is coupled into the opposite connector before being collimated back down to the original beam size and re-coupled into the fibre. Since the beam size is expanded by as much as 40 times, the influence of a 0.02 mm

ferrule-based connectors is reduced by 40

times in a pair of expanded-beam connectors. It is this eect of collimating and greatly

increasing the optical beam diameter that results in the connector being less sensitive to small particles of dust or other contamination, which could completely obscure transmission in butt-joint type connectors. The aluminium shell housings of these expanded-beam fibre-optic connectors have a hermaphroditic mating design which means that there is no possibility for mismating. As a result, they allow easy “daisy chaining” of end-to-end terminated cable assemblies in accordance with the allowable power budget. This means that multiple mating can be achieved, supporting repeated temporary outside- broadcast field installation conditions to an IP 68 protection degree. HARSH ENVIRONMENTS Such expanded-beam FO cable assemblies can be safely applied even in the harshest of conditions. For example, even the unmated open face of a lensed connector can be totally immersed in mud and this will cause minimal damage to the optical faces within the insert. The aected open



ISSUE 12 | Q1 2018

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