Introduction to Fiber-Optic Lighting - Design Considerations
by Craig DiLouie and Randy Smith

Below are several design considerations related to fiber-optic lighting: Brightness/Light Levels In many applications, the lighted fiber-optic material is meant to be seen, not see with, meaning that it must be bright enough to be visible at the desired intensity and distance. Examples include side-emitting architectural detailing and "starry" ceilings. In other applications the material is used to perform a task.

The required light level generally determines what type of light source should be specified and the size of the individual fibers. Manufacturers publish attenuation information, a factor representing light loss per foot over the length of the fiber from its input end to its output end. The quality of the fiber plays a large role here. Attenuation rates have been steadily improving to achieve higher light output levels through better fiber construction and optics.

Light loss factors include the efficiency of the illuminator in concentrating light into the fiber's input end, absorption by filters and color wheels, the efficiency of the fibers, the length of the fiber, dirt and dust, and severe bending. The IESNA and NEMA have published a standard for photometric testing of fiber systems to provide standardized data related to performance characteristics such as light intensity over the fiber's length. This is an enormous step in the right direction in building confidence in fiber-optic lighting among specifiers.

The next step will be for the IESNA to publish a recommended practice guide to this technology. Fixtures The limit of how many fixtures can be fed by a single illuminator depends on the manufacturer. Where light levels are based on brightness as opposed to performing a specific task, up to several hundred fixtures can be supplied from a single illuminator.

Other considerations regarding fixture selection include whether a decorative element is desired, other aesthetic preferences and, for accent and wall wash applications, the distribution of light from the fixture. Bending As stated earlier, be sure not exceed the bending tolerance of the given fiber or it may break or impair its ability to transmit light. Color Shift Some types of plastic fibers can experience color shift to yellow, while certain other plastic fibers and low-quality glass fibers can experience color shift to green as the light is transmitted through the material, which may pose a problem for some applications.

The degree of color shift is based on the length of the fiber. If these fibers are used, shorter lengths or fiber can be specified, or a color-correcting filter. Assembly The fiber-optic system can be specified as a complete system or as individual components that can be assembled at the job site.

Communication Talk to the manufacturer and discover all performance characteristics, tolerances and limitations of its product being considered. Attempt to gain knowledge from product managers and sales reps who have experience with fiber-optic lighting specification and installation, and also from other designers who work with the technology.

Mockup A mockup of a fiber-optic lighting installation can help visualize and test its performance, calibrate the design to actual performance, and sell the technology to the owner or senior management. The Lighting Design Lab, for example, provides mockup facilities.

Installation Fiber-optic lighting systems sometimes encounter problems at the job site. If plastic fibers are to be cut, the cut must be very clean. The fiber ends should also be polished. Some designers who specify fiber-optic lighting have become turnkey installers.

Are Fiber-Optics For You? Fiber-optic lighting has made serious inroads in specialty and accent applications but has had a difficult time competing with conventional light sources in other applications due to fiber-optic lighting's typically relatively higher cost and lower light levels. Unfortunately for this system, energy savings, if any, derived from its adoption is unlikely to produce a satisfying return on investment and therefore energy savings is not a powerful driver in considering fiber-optic lighting.

Specifiers may find that an ambitious installation can produce a budget line item that draws unwanted attention. However, for numerous applications, from hard-to-reach signage and architectural detailing to displaying UV- and heat-sensitive objects to wherever neon is currently used to others, fiber-optic lighting may provide an excellent solution; in museums, for example, fiber-optic lighting may be the optimal solution for lighting archival documents. And there always appears to be an oo-ah factor associated with this highly creative technology.

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Above: example of outdoor fiberoptic back lighting.

Image courtesy Fiberstars