How does cold weather affect fiber optic connectors and cables?

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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.