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Fibre optic cables: Benefits to industry

04 March 2013

In this article Justin Leonard, director at igus UK, reviews how fibre optic cables, particularly those used in dynamic applications, are helping plant managers to operate their factories more efficiently

In this article Justin Leonard, director at igus UK, reviews how fibre optic cables, particularly those used in dynamic applications, are helping plant managers to operate their factories more efficiently

With increased demands for industrial plants to operate more efficiently, managers are reviewing the communications and cabling systems used throughout their facilities.

There is increasing network convergence between design and manufacturing functions, ie between the office and plant floor.

In addition, plant environments are gradually migrating away from proprietary protocols to the most prevalent current standards that use Transmission Control Protocol/Internet Protocol (TCP/IP) and standard Ethernet network structures. The future trend is toward implementing Industrial Ethernet as the linklayer protocol to one of the legacy protocol applications, and ultimately Industrial Ethernet right down to the device level on the machine.

Common Industrial Ethernet protocols, including EtherNet/IP, Profinet and other conforming open systems are already proven in automation applications that require realtime performance and multiple communication channels on the same network. Industrial Ethernet today predominantly uses twisted pair copper cable but fibre optic cabling is also making its way onto the plant floor as it provides a more reliable transmission over longer cable lengths.

In a dynamic application - that is, an application where a cable is used to connect moving parts of a machine - cables may have to move horizontally, vertically, or even with a twisted motion, often carried within energy chains. In today's high performance machines, these movements typically take place at high speed and it is common for them to be repeated thousands or even millions of times in a short timescale.

Fibre optic cabling The benefits of fibre optic cabling are well known in consumer and business communications - such as a higher bandwidth - and it has already been installed in commercial premises. But what additional advantages are there in an industrial setting? Fibre optic cables are smaller, lighter, have higher data rates, longer cable length, and better EMC safety, all enabling plants to operate more efficiently.

The travel length of fibre optic cable is minimally restricted by the transmission system used and can be several hundred metres long. In addition, with a properly designed dynamic fibre optic cable, the increase in attenuation even at very high cycle rates in energy chains is so low that the value is often difficult to measure; any increase in attenuation to be found is usually near the plug.

The question of how much the attenuation behaviour changes has been answered following a series of tests at the igus Technical Centre.

Taking into consideration that standard ST* plugs have a mean insertion attenuation of 0.3dB and a maximum insertion attenuation of 0.5dB, measured results showed an increase in attenuation of approximately 0.1 to 0.15dB - after more than 30 million cycles in the chain this increase is negligible.

Fibre optic cabling provides safe data transmission as it has no sensitivity to electromagnetic interference. As a result, there is no risk of possible data loss.

By installing fibre optic cables, engineers can future proof any bus system. Fibre optics is not bus-protocol dependent, so when the plant eventually changes to Industrial Ethernet from proprietary bus systems, no new cable installation is necessary, saving valuable time and costs.

Fibre optic cables weigh less than their copper equivalents, which in turn means that less energy is needed in the energy chains to move the cables.

A cable with a smaller dynamic bend radius (the minimum radius a cable can be bent repeatedly) has many advantages as it allows plant managers to save space. A smaller bend radius can sometimes be achieved using fibre optic cabling, for example, igus chainflex optical fibre cables can reduce the required bending radii by more than 50% against the similar standard bus cable.

A new generation of dynamic cables, such as igus' chainflex has been designed to overcome this challenge and presents a practical and reliable solution. chainflex fibre optic CFLG.2LB cables are lighter, allow higher data rates, smaller bend radii, longer cable lengths, better EMC safety and show lower damping. In addition, optical fibre cabling is system independent and futureproof - in case of a change of bus system, no new cable installation is required.

This dual-fibre fibre optic cable is designed specifically for energy chain applications, where extremely small bending radii and high cycle life are expected without loss of data. The fibres are designed to reduce the minimum bend radius from the traditional 10x the outside diameter of the jacketed cable to 5x, or only 40mm. Because of the matched length of the fibre optic cores and the aramid strain and torsion relief, more than 8.5 million double strokes have been proved for energy chains in a 38mm test set-up.

Where traditional copper bus cables are still required, igus chainflex bus cables provide a constantly high data quality in applications with permanent movement. With different shield materials such as, PUR, TPE and PVC, cable lengths (to 400m) and torsion angles (to ±180°/m) they guarantee operational safety for almost every moving application. Advantages include: high transfer capacities, mechanical stability and high EMC safety and durability.

With the help of data from two billion test cycles per year performed in the igus test laboratory with more than 1700m2, the lifetime of almost any cable of the chainflex family, copper or fibre optic, can be precisely predetermined.

Provided that such genuine dynamically flexible cables are used and that they are selected and installed correctly, solutions of this type are safe, reliable and cost effective.

It is clear to see that with increasing volumes and speed of data, fibre optic cables are now providing real advantages in industrial applications, enabling plant managers to operate their factories more efficiently.

*ST is a trademark of Lucent Technologies