In the decade since fiber-optic lighting was first introduced here [in the late 1980s] in the United States, we have seen the dramatic development of remote-source systems employing a variety of fibers and light guides. New technologies, some only recently announced, include new lamp designs, advanced optical control, more fixture options and greater economy, while breakthroughs in color addressability, switching, and dimming are yet to be made public. This provides today's lighting designer with options and opportunities not available until now. Remote-source lighting systems are ready to take their place alongside downlights, troffers, and bollards in the designer's tool belt.
While technology continues to expand, [the industry's] standardization efforts have been consolidating a common vocabulary, calculation procedures, testing methods, and specifications. The lighting designer will be able to use remote-source lighting in many new applications, from the replacement of traditional lighting systems to applications where lighting was previously not possible. As any developing technology creates new opportunities, it also creates new challenges in making educated choices about products, materials, and applications.
Learning the Lingo
The first successful effort at standardization has been in establishing a common vocabulary. Below is a partial list of key terms essential to understanding and talking about remote-source lighting (source: IALD Lighting Industry Resource Council, Remote Source Lighting Committee):
Light Guide: The material used to transmit light from the light source, typically bundles of plastic fibers, with glass fibers less common in the United States. Light guides may be side-emitting, like neon, or end-emitting, supplying light to fixtures such as downlights.
YARNELL'S THOUGHTS: Fiber-optic lighting is not dead, but it is no longer perceived by the lighting community to be the hot new technology that it once was. Just a year or two after this article was written, the buzz at Lightfair was all about fiber optics. Many companies were investing in it, designing fixtures and illuminators, and carving out niches in the lighting marketplace with specialty products. Companies took stands in their product approaches: plastic versus glass, white light versus color-changing, and miniature versus high power, but fiber optics as a mainstream lighting product never reached its full potential. Even in the economic boom of the '90s, the cost and payback analysis rarely worked for commodity applications and general lighting. The lamp companies didn't really want to promote a single light source that was designed to replace dozens of sources, and automobile companies (which were initially thought to be the leader in fiber-optic lighting) began tinkering with LEDs for taillight applications.
Looking back, we can identify a number of things that made it difficult for fiber-optic lighting to take off. First, it required a whole new method of calculation and design. One had to take into account splitting initial lumens into multiple fibers, accommodating for light absorption over the length of the fibers, and color shift as light bounced off of the fiber perimeter and through the plastic or glass. Second, it took the combined investment of many companies just to even scratch the surface of the new technology. Millions of dollars were invested into building the right illuminator and improving on the best fiber technology, but without the big lamp companies on board, backing for these specialty lamps soon lost out to the new fluorescent and ceramic metal halide (CMH) technologies that were being pursued by the larger manufacturers, especially when it came to downlights. Third, small companies could not afford to invest in all of the different fixture designs that lighting designers desired. Fourth, the small manufacturers that took on fiber optics ultimately were not large enough, nor did they have large enough marketing budgets to compete against the commodity manufacturers with cost-effective, common light sources that didn't require additional education on the part of the lighting community. (Additionally, most of them [the smaller manufacturers] had internal design teams to assist lighting designers when planning an installation, which added to the cost and overhead of the companies.) And finally, the limitations of fiber optics as a general light source required much more to overcome technically than the small fiber-optic lighting companies could handle.
A colleague told me that I should just say “never mind” and be done with it, but there are many lessons to be learned from fiber-optic lighting's attempt to go mainstream. Small companies that partnered with larger lighting companies for their marketing strengths disengaged a short time later and redirected their efforts into LED specialty lighting, which was just starting to emerge on the architectural lighting scene. Some manufacturers saw LED as a compatible sister source and offered the two technologies in combination for specialty applications. Others found no way to pay back their investors and, in lighting terms, “faded slowly to black.” Larger companies that dipped their feet in the fiber-optic pool have tried many technologies in the ensuing years: electroluminescence and flat-panel fluorescents, miniature cold-cathode lamps, flow-neon, sulphur lamps, and many other technologies. And each company has boasted that its technology would be the next best thing since the invention of the incandescent lamp. Some of those technologies found their niche, others have not.
So what do I put my money on these days? LED sources, of course. They have a lot going for them that fiber optics did not. There is greater financial backing from across multiple industries—semiconductor, electronics, TV, automobile, toys—as well as venture capitalist support. Plus, the cost of LEDs is relatively low compared to fiber optics, and paybacks are achievable. Many of the technological hurdles of fiber optics have already been overcome by LEDs; the source can be used for niche applications such as color-changing, as well as commodity products such as downlights and troffers, parking lot and landscape lighting, and decorative and industrial lighting. Additionally, LEDs have benefits such as long life, energy savings, relatively cooler operation (when coupled with the appropriate heat sink) than filament sources, and are small scale, which allows them to be applied in many different ways. In 1984, when I designed my first high-rise office building with T8 lamps and electronic ballasts, I was taking a risk. Looking back, I took no more of a risk than I currently see in using LED sources for general lighting applications today. Almost 30 years later, and hundreds of technological advancements hence, the lighting industry is still finding new ways to solve our lighting needs, and the entrepreneurial risks are often the ones that get us, eventually, to a mainstream solution.
Kennneth Yarnell is currently the director of architectural interior accent and specialty for Cooper Lighting.
Illuminator: The “black box” that houses the light source and injects the light into the input end of the light guide. Other components include any necessary transformers or ballasts: reflectors, refractors, or lenses to control the light beam; cooling devices; color filters and controls; and mechanical connectors to attach or align the light guides. The efficiency at which the illuminator injects light into the fibers is called optical control. The aperture(s) through which light is released are called ports.
Connectors, Couplers, and Ferrules: Devices used to join parts of a system physically or optically. Connectors hold a fiber or guide to a port, fixture, or other guide. Couplers align the guides to each other or the illuminator. Ferrules are termination devices typical to glass-fiber bundles, and are used to keep fibers properly positioned relative to each other. Main ferrules are larger ferrules used to harness groups of fiber for insertion into a port.
Fixtures (Fittings): Outlet devices applied at the end of each guide used to distribute light for end-emitting light guides.
The first specification decision will be choice of the right light guide. Small plastic fiber (SPF) and large plastic fiber (LPF) are most common, although glass-fiber bundles (GFB) are common in other countries. For brevity, we will focus on plastic fiber. The design need will dictate the most appropriate material and size.
SPF is often manufactured as a raw product distributed to original equipment manufacturers (OEMs), who in turn add value in bundling, harnessing, sheathing, and scoring. The result is a unique product available to the designer, which is typically patented. SPF bundles can be used to supply fixtures such as downlights, landscape lights, and roadway pavers.
LPF is distributed similarly as SPF, with some products being cast and others extruded. Core materials vary and will be suitable for different applications. Side-emitting products vary considerably in output and allowable run lengths, and end-emitting products experience various color shifts and attenuation rates over their lengths, which may affect an installation. LPF can be configured to perform almost any of the same applications as SPF.
Efficiency and installation are important selection factors. While considering the efficiency of the light guide, the designer should also assess the following: one, the beam spread and focus of the lamp; two, the angle of acceptance of the fiber; three, the position of the fiber in relationship to the source; four, the fiber-optic connection or building process, including polishing, aligning, and the percent of unused face area; and five, efficiencies of splices and fixtures.
Regarding installation, consider cost, size, packaging, and simplicity: Splitting, splicing, and joining technologies now under development will allow reduced fiber runs and decrease installation costs. Field-installation techniques are becoming simplified with the introduction of more-complex acrylic-fiber materials with fewer environmental limitations. In addition, the larger size of LPF fiber optic negates the need for factory bundling.
Halogen and high-intensity discharge (HID) metal halide lamps are common in remote-source lighting. Selection will be based on light output, color size, service life, and other factors. In systems now under development, backup or supplemental light sources will be easier, less costly, and more effective.
“The small manufacturers that took on fiber optics ultimately were not large enough … to compete against the commodity manufacturers with cost-effective, common light sources that didn't require additional education on the part of the lighting community.” — Kenneth Yarnell
Halogen lamps from Europe offer long life and precise beam control from tiny filament sizes, providing continuous spectrum lighting. An Australian manufacturer has produced a small halogen illuminator with hose-down capabilities and fanless convection with no breakdown of the plastic fibers even in areas with high ambient temperatures, ideal for outdoor applications.
HID lamps have also seen advancements. Compact sizes permit greater optical control. One manufacturer offers compact 60W xenon metal halide lamps with instant-start capability and a tiny arc gap. The integral reflector provides precise beam control for use in harnessed fiber applications. Other 150W small arc gap metal halide lamps are also common. One manufacturer adds a dichroic reflector to the most common lamp, positioning the arc tube within each reflector to provide optimum performance and beam angle for the specified type of fiber bundle.
Fiber-optic lighting is ideal for special effects because it can change colors. Now, addressable color is available. DMX 512 is a common control protocol in the theatrical market, with DMX controllers finding their way into some illuminators. Controls that allow selection, timing, and accurate changing from one color to another—with options for mixing dichroic colors as well as dowsing certain filters—make sequencing of special effects easy, while allowing even more complicated visual effects.
Illuminators are increasing in optical control with improved designs. Illuminators with the greatest efficiency in optical control are most desirable. One manufacturer provides individual fiber connections with focused beams of light into each fiber, allowing the easy field installation and consistent light output. As for fixtures used with end-emitting guides, a continually growing number of standard designs are available. Designers have the ability to design their own fixtures—there are no electrical components to worry about, recessing depth problems, or UL hassles.
Writing the Spec
The designer may write a performance or manufacturer's spec. Performance specs may provide the most competitive situation for the client, but they are not always most practical. Manufacturers do not provide the same information, for example, so comparative analysis in the construction administration phase may not be easy.
When writing a performance spec, the designer should consider various light sources and their color rendering, color temperature, color consistency from guide to guide, color shift over the guide's length, and the illuminator's optical control, which affects color and light output consistency. When special effects are desired, note that systems are continually developed; knowing what is coming to market can affect how a spec is written.