Offering another tool for creative illumination, you can easily grasp fiber optic lighting technology if you understand some basic concepts.
Fiber optic lighting continues to interest electrical contractors because of its complexity. As this technology continues to mature and find more applications, recent efforts of industry professionals to create a common vocabulary, calculation procedure, and testing methods will help reduce installation concerns.
At the same time, the introduction of more complex acrylic fiber materials, which feature fewer environmental limitations, continue to simplify field installation techniques. In combination, all of these activities will inevitably drive up the demand for fiber optic lighting.
A variety of components make up a complete fiber optic lighting system, including the illuminator, light guide, port, connector, coupler, ferrule, and fixture. Let's take a closer look at each.
Light source. The size of the individual fibers and the required illumination level generally determines the wattage and type of light source to use. The ideal lamp for fiber optic lighting is one with a very small area of light generation and high lumen output. A reflector located behind the light source and a lens in front of the light source help to deliver light efficiently into the optical fiber.
Commonly used lamps include 20W to 75W low-voltage MR16 lamps and 70W to 250W metal-halide (M-H) lamps. MR16 tungsten halogen lamps offer precise beam control from tiny filaments. However, some new compact M-H lamps offer similar tight optical control.
Illuminator. The power unit that houses the light source for the fiber optic lighting system is called the illuminator. Constructed of sheet metal or high impact plastic, we sometimes call the illuminator the projector, see photo on page 32H. You can fit the illuminator with filters to remove most infrared (IR) and ultraviolet (UV) energy emitted by the lamp. Thus, a fiber optic lighting system is ideal for illuminating textiles, paintings, and food products.
You can also fit an illuminator with a dichroic glass color filter wheel to provide a continuous or fixed change of color as the light passes from the lamp to the fiber end. Additionally, you can computerize the movement of a color wheel to provide special effects, such as timed light changes or strobe-like bursts of light. Finally, you can link several illuminators in tandem or series for powering complex installations.
Light guide. The material used to transmit the light from the light source to the fixture is known as the light guide. Typically, these are bundles of plastic or glass fiber, which we also call tails.
The basic materials of a fiber optic light guide are the core and cladding. The core is the component that transmits the light. Tightly fitted around the core, the cladding is a thin material with a low refractive index. Light beams that graze the cladding at shallow angles reflect back into the core.
Most optical fibers have a third protective jacket, which is black, clear, or translucent white. We use fiber with a black, nontransparent jacketing with end-emitting fiber. We use clear or white jacketed optical fiber with side-emitting fiber, which looks like neon lighting, or with linear emitting fiber that we use in a manner similar to fluorescent lighting.
Fiber optic cabling is made with three materials:
• Large core plastic fiber. A solid polymer fiber, up to 20 mm in diameter, which is clad with a thin material having a lower refractive index than the core.
• Small core plastic fiber. A solid polymer optical fiber, up to 2 mm in diameter, which is clad with a thin material having a lower refractive index than the core. It comes in any length, and you can field cut it. Essentially, these two types of plastic fiber perform similarly and have the same environmental limitations.
• Glass fiber bundles (GFB). A circular light guide made of glass with a diameter between 0.002 in. and 0.006 in. (about hair thickness).
Glass fiber, which is usually the end-emitting type, has particular advantages including the fact that glass material does not lose its transparency (become yellow) over time. As mentioned above, the glass tails are much thinner than plastic. Unlike plastic fiber bundles, which you can field cut, glass fiber harnesses typically come factory cut and assembled.
Fiber optic port or master ferrule. A metal or plastic connector attached to one of a fiber optic bundle, allow you to insert it into an illuminator for maximum light output. A manufacturer can assemble the bundle (called porting) before shipping or you can do this in the field to suit changing conditions.
Connectors, couplers, and ferrules. We use these devices to join parts of a system physically and/or optically. A connector holds a fiber to a port or fixture. A coupler aligns a fiber to the illuminator or two fibers to each other. A ferrule is a terminating device used to keep a fiber bundle properly positioned. Ferrules usually come factory designed to work with particular fibers, so you simply insert the ferrule into the fixture's connection sleeve.
Fixtures. Due to the large variety of fiber optic fixtures, it's hard to know which one to use. However, most are application specific and include:
• Downlighting-type fixtures generally consist of molded plastic or cast aluminum and come in a variety of designs and finishes. The manufacturer usually puts a nonadjustable lens into the housing to provide some type of beam focusing. Their small size and flexibility in relation to the possible mounting positions means you can use a downlight fixture almost anywhere.
• Wall washer and accent fixtures. Often referred to as eyeballs, these fixtures are adjustable by means of a socket for easy aiming. Many include an adjustable lens that allows the light to focus from narrow to wide beams. Many people use accent fixtures, with a variety of beam shapes, in showcases or displays.
• Landscape and exterior fixtures. Units come in a variety of designs for illuminating a landscape, sidewalk or garden, and many use decorative elements in landscape-type fixtures.
• Underwater fixtures. The absence of electrical components makes fiber optics an ideal choice to illuminate swimming pools, whirlpools, fountains, and similar locations.
• Specialty fixtures. An assortment of miniature fixtures, fitted with shaped clear, colored or frosted glass, provides tiny points of light -- thus serving a decorative function in a ceiling or elsewhere.
• Custom fixtures. Since fiber optics lighting lacks any electrical restrictions, you can mount fiber bundles in various materials, including furniture, handrails, and artwork.
Equipment installation. As with all types of fixtures, you must provide adequate space around the light source to dissipate heat from the lamp. Many illuminators use an internal fan to provide air circulation.
Spring clips, screws, or adhesives hold many end-emitting fixtures in place. Fixtures used in display or showcase applications are just as easy to install. If you use mounting rails, manufacturers can cut them to the correct length for easier use at the job site. Individual fixtures either click or slide into the desired locations on the rail.
Make sure you don't bend the fiber tails beyond the manufacturer's recommendations. In general, you can bend glass fibers up to 10 times the diameter of the light guide. If you bend glass fibers beyond 90 degrees, some of the individual fibers might break, thus reducing light output.
Advantages of fiber optic lighting? You can install a fiber optic lighting system almost anywhere. The thin optical fiber cabling fits into the ceiling or wall of almost any existing structure.
Fiber optic lighting is perfect for historical structures when you can't penetrate existing material. You can retrofit original lighting fixtures with fiber optics and recreate historic light levels and color.
Since there is no electrical power in the vicinity of the light-emitting parts (a safety consideration), no electromagnetic fields exist. Thus, you can use a fiber optic system in areas with EMI sensitive electronic equipment, such as a magnetic resonance imaging room.
