Abstract (summary)
Why use fibre optics?: The most obvious reasons to use fibre optics in industrial facilities are usually related to their excellent physical properties such as immunity to electrical noise and the ability to transmit large amounts of data. Less known but perhaps more importantly, fibre optics provide a single medium for a wide range of communication needs. For example, one fibre cable bundle can provide for the transmission of computer data, as well as communication between field devices and controllers, video images, voice, security and fire alarms. No other single type of cabling offers a communications pathway to such a wide variety of equipment.
Single-mode fibre is an optical glass fibre with a core diameter so small it has only one mode for light to travel. It is usually a fibre with a core size between 8 and 9 [Symbol Not Transcribed]m. Because of this straight path dispersion is almost zero. Single-mode is used in applications requiring long distances (up to 120 km) and extremely high bandwidth (10 Gigabits/sec), but the small diameter makes terminating and connecting difficult. It is rarely required today in industrial applications. Nevertheless, some engineers are including two or three pairs of single-mode fibre in multimode cable bundles to future-proof the design.
The cable selected was a tight-buffered 62.5/125[Symbol Not Transcribed]m multimode fibre. This tight-buffered cable was rated for both indoor and outdoor use and had an FT-4 flame rating. The tight-buffer significantly reduced the connector installation costs. The fibre count in the cable was initially design to be 12 fibres. However, the realization that the fibre would likely be used for both PLC and DCS highways and I/O, closed circuit video and the mill computer network soon pushed the fibre count to 24 fibres. These 24 fibres were split into two 12 fibre aluminum interlock armoured cables. The separate cables were easier to handle for installation and allowed some extra measure of redundancy.
