Illumination: Fibre optic lighting in signs and displays

The ability to create and install illuminated displays in new forms and locations is due to the attributes of the components, including the optical fibres, the light source and the related hardware and fittings.
Photo © Schott North America

Light sources
There are, as mentioned, three main types of light sources for fibre optics: LEDs, metal halide and halogen.

The lifespan for halogen lighting ranges from about 1,500 hours for a 100-W lamp to approximately 3,000 hours for a 20- to 75-W lamp. Metal halide lamps, meanwhile, are rated to last 6,000 hours.

LEDs, on the other hand, offer a lifespan of up to 50,000 hours, drastically reducing maintenance costs by maximizing the duration of operation before any bulbs need to be changed. Further, they offer brightness levels equivalent to 100 halogen lamps, save energy, contain no toxic mercury and—thanks to low levels of heat—support the use of plastic fibres instead of glass.

For these reasons, LEDs are increasingly being adopted as light sources for optical fibre-based signage and display applications.

Fibre cables
With no heat or electricity running through them, optic fibre cables are very safe and virtually unbreakable. Thanks to these attributes, they can eliminate many typical restrictions when it comes to designing sign lighting systems.

Optical glass fibre for illumination applications is typically available in a variety of standard bore diameters, ranging from 0.75 to 14 mm (0.03 to 0.55 in.), with wider sizes available for more challenging applications. Multiple diameters can be combined within a single harness, as can varying lengths. The number of output points that can be generated from a single source will depend on the total combined bore diameters of all of the light guides within a system.

Unlike light sources (even LEDs), optical fibres do not lose their light intensity or burn out. So, while an illuminator can experience a reduction of intensity and even a burnout over time, the ability of each individual optic fibre to emit light through its ends or sides will keep on going.

The fibre optic system for a series of halo-lit channel letters at Dubai International Airport in the United Arab Emirates (UAE), for example, comprises a total of 6,000 m (19,685 ft) of end-emitting optic cabling and 130 illuminators with 150-W metal halide lamps. Each letter in the outdoor sign—which spells out ‘Emirates Engineering’—is 2.7 m (8.9 ft) tall.

Fibre optics can carry light from a single source to multiple points, so as to illuminate a large area.
Photo courtesy Luxam

Side-emitting cabling provides a lower-maintenance, higher-durability alternative to neon or chain lighting. It is suitable for use in water, icy conditions and other extreme weather. It is available in an ultraviolet-stabilized (UV-stabilized) form and treated with algaecide and fungicide.

Non-glass options include polymethyl methacrylate (PMMA) solid optical fibres, such as the aerospace-grade products from Nouvir Lighting, which use the same material found in jet fighter’s canopies, reportedly will not yellow and have been measured to lose only 0.7 per cent of light for every 0.3 m (1 ft) of length. Unlike many glass-based fibre optics, acrylic can remain opaque to both infrared (IR) and ultraviolet (UV) radiation and cannot transfer heat to sensitive displays (such as the exhibit cases in museums).

With all of these options available, it has become much easier today to avoid the environmental effects that would typically harm copper cable. And as optical fibres do not conduct electricity, they can also prevent problems with ground loops and conduction of lightning.

Learning from other markets
Given how the use of fibre optics in signage is still relatively new and not yet widely offered in the sign industry, it is fortunate other well-established lighting applications can provide a helpful ‘test bed’ for how signs might be illuminated in the future.

One important factor, as mentioned, is weight. In the automotive and aviation industries, the lower weight of materials translates into better mileage. With aircraft, especially, weight is a critically important factor in performance.

With fibre optics, weight savings come not only from the fact the material itself is light, but also because the system as a whole can use less copper wiring and far fewer individual lamps, other than the illuminator(s).

In medical and surgical applications, fibre optics for minimally invasive procedures have brought light into places it was previously impossible. Similarly, the technology allows signs to be illuminated in what were previously difficult environments, such as in the middle of a rushing fountain.

Museums, meanwhile, have led the way in taking advantage of fibre optic lighting’s colour temperature. Light-based radiation can act as a catalyst for oxidation, which is particularly problematic when illuminating an exhibit of organic artifacts.