How does cold weather affect fiber optic connectors and cables?

At the speed of light, it carries huge quantities of data at the speed of light – optical fibre is everywhere. Flexible and thin, around the thickness of human hair, glass or plastic fibre is super-fast.

Overtaking copper wire as the medium of choice, fibre carries data as pulses of light. Because of its lower cost, its faster speed and the fact it’s less bulky is the reasoning behind the shift. Optical fibre is also harder to hack than copper, making it more secure and safer because it doesn’t generate heat in the same way copper does.

It does, however, come with its own challenges. Installation and management must be carefully managed because of the delicate nature of optical fibre. Any amount of grease, dirt or moisture can affect the transmission of light, even the tiniest of specks. Although the actual fibres themselves are protected by and acrylic layer, the connectors joining each fibre can be vulnerable in harsh environments.

This is true in outdoor applications such as FTTx, data and telecommunications, civil engineering, broadcasting and marine. It is imperative that the optical fibres are robust enough to cope with being run between communications masts for telecoms links, across freezing ground for television outside broadcasts, and alongside roads to carry video from traffic cameras.

Freezing temperatures causing damage

The way that fibres and connectors deal with sub-zero temperatures is a significant problem. Water can end up making its way into the duct carrying the fibre or the conduit. This is usually the case if there are any gaps or more commonly, imperfect joins at the connectors. In fact, standard interface connectors are not simply not robust enough to avoid water ingress in harsh environments.

When the temperature drops sub-zero and water freezes, and ice forms around the fibre – this causes the fibre to deform and bend. This then degrades the signal passing through the fibre, at the very least reducing the bandwidth, but quite possibly stopping data transmission altogether.

To mitigate this problem, one approach is to only install fibre cables buried below the frost line, so there is no threat of ice. But this solution can be extremely expensive and is difficult to follow when cables need to be routed along a bridge or other structure. Another solution can be to add antifreeze liquids or gels to the fibre conduit, but again this can have a high cost.

Rugged connectors

To cost-effectively protect an optical fibre against extreme temperatures, it is essential to protect not only the connections but the end points from any water that can get into the conduit, and go on to freeze.

A connector that is specifically designed for harsh environments can ensure that the fibre conduit is sealed, therefore, keeping the fibre itself safe from the risk of ice formation.

There are three common types of fibre connectors: SC, ST (bayonet-twist) and LC (push-pull locking). The LC connector is most commonly chosen, because it is much smaller than the other two, and also provides a secure clip connection.

Unfortunately, a standard LC connector does not give the same type of protection that a rugged connector does and does not provide sufficient protection against water ingress. Although it is possible to build a custom enclosure that will protect the connector, it can prove to be very bulky and is not cost-effective.

Instead, a much better approach is to specify a rugged LC connector that is specifically designed for harsh environments. For example, Bulgin’s 4000 Series Fiber connector is the smallest sealed standard interface connector on the market. The fibre connection is UV resistant, salt spray resistant and sealed to IP166, IP68 and IP69K, while still providing an industry-standard LC interface as specified by IEC 61754-20.

The connector and its housing can be completely immersed in water up to a depth of 10 meters, for a period of up to two weeks (based on IP68 rating tests), without allowing water to gain access to the conduit and hence potentially to freeze and damage the fibre. The connector can also handle temperatures from -25 to +70c and protects the fibre against dirt and dust.

For duplex fibre connections, the 6000 Series Fiber would be more fitting. Like the 4000 Series Fiber, the 6000 Series Fiber connector is suited for outdoor broadcasting, FTTx, server room engineering, civil engineering and aviation & rail applications.

The 6000 series harsh environment optical connector is designed for years of service in areas where unprotected physical contact fibre, isn’t an option. Featuring a secure, yet easy to operate 30 degree locking mechanism, this series has field proven IP68 and IP69K performance.

In comparison to the simplex 4000 Series Fiber connector, the additional glass fibre on this duplex cable can double the data transmission capabilities where required.

With a suitable rugged connector, engineers can now plan their fibre deployments in harsh environments without fear of damage from ice – and without the cost of antifreeze, or the inconvenience of bulky enclosures.

Author: Fiber-MART.COM

eShop of Fiber Optic Network, Fiber Cables & Tools

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