Glass optical fibre is a highly efficient transmission medium that needs careful handling. Trevor Downes reports on a less temperamental solution.

Fibre optic cabling is often crucial for telephony and data services, so an accidental disruption could affect millions of people.

However, most of us never get close to these ‘backbone’ fibre optic cables, which have many uses besides telephony and data.

Optical fibre has usually been made of glass, which offers great transparency and low cable losses. Signals can travel many kilometres before requiring any error correction or boosting.

But glass optical fibre is reasonably fragile and needs to be handled with care. Such cables are subject to strict bend-radius procedures and are quite technical to terminate in the field, requiring thousands of dollars of tooling to make reliable and functional joins, splices and terminations.

Plastic optical fibre (POF), similar to fishing line, is also available on the market. It is easy to terminate and join in the field (like hooking up speaker wires to an amplifier), flexible and reasonably robust.

The material cost is low, thereby reducing capital outlays. When this is combined with reduced termination and tooling costs, POF starts to make sense.

Glass fibre is widely used in computer networking, generally between switches and other hardware. The last link to the end user is typically via a copper connection using a Category X type cable and RJ-45 connectors.

Fibre is also widely used as a transport method for web traffic, across cities, states, countries, continents and oceans. Free-to-air and pay-TV operators use substantial amounts of fibre for their day-to-day transmission operations, and for outside broadcasts communicating with the studio.

Our much-publicised National Broadband Network is primarily fibre. In most cases it will be fibre to the premises, offering higher speeds and improved reliability over DSL copper-based delivery.

Apart from networks and data, fibre has quite a few other uses, including signage, medical illumination and effects. Such applications typically use polymer fibre.

Another common use of fibre is the TOSLINK cable, which has been around since the early 1980s. Designed by Toshiba, the TOSLINK receptacle is generally included on Blu-ray devices, set-top boxes, pay-TV boxes, media players and Apple TV, to name a few.

Even though they may not realise it, a lot of people are familiar with this type of fibre, which allows the simple connection of multi-channel digital audio to receivers, amplifiers and displays.

Thinking of other uses for fibre brings me to the professional audio-visual sector and the residential market. Fibre has such huge bandwidth (think of it as a big pipe) it can be used to send all sorts of digital data and lends itself beautifully to the transmission of digital video.

There are fibre solutions for all digital video formats:

• HD-SDI, used in broadcast and post-production environments;
• DVI in single and dual link, widely used in corporate, educational, industrial, military and home applications;
• DisplayPort, which seems to be gaining momentum; and
• everyone’s favourite, HDMI.

These products take the following configurations:

• complete cable assemblies, with end connectors fixed to the fibres, and manufactured in predetermined lengths with detachable ends in either a small form factor transmitter and receiver; and
•  box-type enclosures.

There are a few of advantages when using detachable products:

• You can buy the connectors cheaply and do the installation just as you would with conventional cable, fitting them later in the project.
• You can replace the ends easily should they be damaged by storms or other electrical causes.
• And because the fibre is a big fat pipe, when new higher-resolution technologies come onto the market you can change the ends quickly and easily.

Fibre cables with fixed ends should not be installed where they might be difficult to remove. They contain electronics and are susceptible to external damage, so you certainly would not use them inside plaster walls without ensuring easy access.

One key advantage in using fibre for digital video is complete electrical isolation – there is no danger of ground or earth loops interfering with your image. Signals are pixel-perfect from source to display over distances up to 30km for HD-SDI, 1000m for single-link DVI, 500m for dual-link DVI and up to 1000m for HDMI.

If you need to send digital video over long distances without risk of image degradation, then fibre optic is the clear choice.

POF is widely used in industrial applications, and also for in-car networks in the upmarket brands. This linking of various devices in the vehicle is called media-orientated system transport or MOST.

The uptake of POF in the residential market has been a struggle for most vendors, the primary reason being network speed, which is limited to 100Mbps.

Recently there have been developments to increase the network speed to 1000Mbps, matching the best copper systems. However, associated products are still under development and scheduled for release later in 2013. When this happens, POF will get a boost and should be revisited as an alternative to Category X cable network infrastructure in many markets.

POF has such a small diameter it can be run under carpet or tucked under skirting boards, making it ideal for retrofits or getting to difficult locations.

Termination for some devices is as simple as using precision scissors and inserting the cable into a connector in a similar manner to speaker connectors. There are also field-terminable connectors that are quick and easy to apply with a basic tool kit. They are easier to terminate than an RJ-45 connector.

As the NBN is rolled out and the word ‘fibre’ permeates our day to day lives, POF may be the answer for those who want to build a network without the expense and complication of glass fibre.