One of my recent magazine columns focused on a noncommunications use of fiber optics—lighting. In this article, I’ll revisit the topic to flesh out that topic even more, using illustrations to show how fiber optic lighting works and show some examples of the applications.
Fiber optic lighting uses optical fiber as a “light pipe,” transmitting light from a source through the fiber to a remote location. Some lighting uses large plastic fibers like the one above while others use bundles of glass or plastic fibers to transmit more light. The light may be emitted from the end of the fiber creating a small spotlight effect (also called “end glow”) or emitted from the outside of the fiber along its length like a neon or fluorescent tube (also called “side glow”).
The plastic optical fiber above is illuminated by the red laser in a fiber optic visual fault locator, a tool used by almost every fiber optic installer. It shows how fiber can be used for illumination and design. The light is transmitted through the fiber to produce a red-light source at the end. The light lost in the fiber is leaking out of the surface of the fiber making it glow like neon tubes.
Fiber Optic Lighting Components
Optical fibers used for lighting are similar to fibers used in communications, but they are optimized for transmitting light not high-speed signals. The fibers consist of a core that transmits the light and an optical cladding that traps the light in the core of the fiber. Unlike communications fibers that use small cores to maximize bandwidth, lighting fibers use large cores with thin claddings to maximize coupling of the light from the illuminator into the fiber. Side-emitting fibers have a rough interface between the core and the cladding to scatter some of the light out of the core along the length of the fiber to create a consistent lighted look similar to neon light tubes.
End and Edge-Emitting Lighting Fibers
Lighting fibers can be made of glass, just like communications fibers, or plastic. If the fibers are glass, they usually have a very small diameter, and many of the fibers are bundled together in one jacketed cable to provide enough light transmission. Larger diameter plastic fibers are also used, perhaps more commonly, because they are inexpensive and easier to install, but they have higher light loss and cannot withstand heat as well as glass fibers, sometimes limiting the light input from a source.
The light source is usually called a “fiber optic illuminator” and consists of a bright light source and may have some optics to efficiently focus light into the fiber. Sources must be bright, so quartz halogen or xenon metal halide lights are commonly used for larger bundles of fiber. Smaller bundles or individual fibers use LEDs that very efficiently couple light into fibers but do not achieve the light levels of the other lamps used for bundles of fibers.
Here are some examples of fiber optic lighting courtesy of BL Innovative Lighting in Vancouver, British Columbia, Canada. These not only show the flexibility of fiber optic lighting but also the possibilities for creative design. Note their other lighting products include some innovative uses of LEDs.
Designing Fiber Optic Lighting
Designing fiber optic lighting can be difficult since it seems every product is proprietary, and every application is unique. Plus, unlike communications fiber optics, there are few, if any, industry standards. Since there is so much variety in fiber optic lighting systems, it’s hard to generalize about designing systems. However, every design project will start with some common items: what is being lighted, what kind of light is desired (intensity, illumination pattern, color, etc.), any unique design features and where the illuminator will be placed.
There are a few design issues unique to lighting. The attenuation of the optical fiber varies with color, which requires choosing a source color that will be correct after the chromatic attenuation of the fiber being used is factored in. Heat from lamp illuminators may require ventilation. Edge lit systems may require illumination from both ends to get even lighting along the entire fiber.
If the designer is new to fiber optic lighting, consulting with an experienced designer, contractor or manufacturer is highly recommended. They will be able to recommend designs, fiber optic lighting components and manufacturers. They should also be able to help design not only the fiber optic lighting system, but also the electrical power and controller for the system.
The installation of fiber optic lighting systems involves installing cables, illuminators and fixtures. Most of the applications are custom and many will require specialized practices related to the components being used. Working with manufacturers who have not only developed the components but also the installation fixtures and practices is the best way to ensure the installation is properly done. If the application is a new type, experimenting to determine if it will work properly before committing to the actual work may be necessary.
The advice given above about designing fiber optic lighting systems holds here too, as there is no substitute for experience. But any competent electrician able to install lighting should be able to install a fiber optic lighting system, especially since they are experienced in installing cable, light fixtures and electrical power and controllers.
For more information on fiber optic lighting systems, don’t overlook manufacturer or distributor sites as they have many examples of actual applications. Another useful option is “Fiber Optic Lighting” by Russell L. DeVeau.