Illuminating Options

Shutterstock/Jordan Tan

Since optical fiber transmits light, it’s obvious that it could be used for illumination. Put a bright light at one end and most of that light will come out the other end. Many people are familiar with this application because of the widespread use of decorative fiber optic lamps and Christmas trees, but there are many other uses for fiber optics in lighting. Special fibers have been engineered for specific requirements to produce functional lighting.

Fiber is used in many lighting applications because of its unique properties. Since fiber transmits light with low loss, the lighting end of the fiber can be quite remote from the light source. It is possible to place a solar collector on a roof and bring light into a building without adding heat from lamps.

Fibers are made from thin strands of glass or plastic that are flexible and allow light to be found in areas that would be difficult for most lamps. The tiny illuminating end of the fiber can be slipped into small and hard-to-reach spaces to provide illumination. This is especially useful when combined with fiber optics for the visual inspection of hard-to-reach areas such as inside objects, engine cylinders or human bodies. Fiber’s flexibility allows it to be used in other ways too. Fibers have been woven into clothing for decoration, included in artwork and made into unique decorative gadgets.

Since optical fiber, either glass or plastic, is nonconductive, the light source can be electrically isolated from the light itself. This has made fiber optic lighting popular around water, fountains and other underwater applications where electrical safety is a concern.

Since the electrically powered light source is remote, the heat generated is isolated from the light exiting the fiber that allows the bright illumination of objects that could be damaged by heat from conventional lamps.

Museums have always appreciated this aspect of fiber optic lighting because it protects valuable display pieces. A lens can be added on the end of the fiber to focus light in a small spot. This is ideal for small objects such as jewelry and would preclude the need for mounting a large, hot lighting fixture in the same cabinet.

Fiber optic lighting offers simple ways to change the shape and color of illumination. Early systems used bright halogen lamps such as projectors to emit white light. This light could be filtered to any color, and motor-driven color wheels could be used to vary the color over time. Today, light sources are more likely to be LEDs, and some can be programmed for different colors to provide dynamic and varying light displays.

Fibers’ small size makes them useful for pinpoints of light. This allows for the illumination of small objects, but it also enables designers to create starfield ceilings for science museums, planetariums, fancy homes and even the ceiling of a Rolls-Royce.

Fibers used in communication are designed to transmit light with minimal loss. However, engineering the fiber to have high loss allows significant light to exit the fiber surface, which produces a fiber that looks like a neon lighting tube. These edge-emitting fibers are generally flexible large-core plastic, and can be bent into shapes to mimic neon tubes. However, they are much simpler and less expensive to fabricate. Fiber can change colors by varying the source and can make displays with more functionality than neon tubes. Edge-emitting fiber does not require high-voltage power supplies.

Before LEDs were developed for signs and pixel displays, arrays of fiber optics were used with a single fiber for each pixel. The complexity and cost of these displays limited their use, and LEDs became a better choice when they became available.

In fact, that’s one of the primary reasons fiber optic lighting is not used more widely. It has always been more complex and expensive than conventional lighting. LEDs offer low power consumption, many color choices and lower costs. Because of this, LEDs have dominated the lighting market. Fiber is still a better choice in some applications, but competition from LEDs has greatly affected its use.

About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor

Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.JimHayes.com.

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