Most fiber optic systems consist of a light source, a coupling system, and a length of fiber optic material that emits light either where it terminates or continuously along its length. In fiber optic systems the coupling system, with an integrated source and ballast, is housed in what is called the illuminator. The illuminator can be located anywhere within reasonable proximity to the task requiring lighting. Single or multiple solid optical channels are distributed to provide illumination throughout the space or application area. Illuminators can be installed within the ceiling plenum, within a wall, or anywhere else within the space. Most commercial illuminators range in volume from approximately 1 to 2 ft3 and therefore can be mounted easily under a laboratory bench or adjacent to a task surface.
Fiber optic lighting systems can be divided into three types:
1) End-emitting – this type of system uses flux that exits the fiber optic where it terminates, to spot light a surface or a specific task area. Single or multiple fibers can be connected to a single illuminator. At the terminal end of the fiber system, an optic head distributes light to the task area. Commercially available systems allow designers to achieve very tight distribution for spot lighting small areas. Designers can also use wide distribution systems for lighting large areas.
End-emitting systems are particularly suited for environments where the demand for light is highly specific or task oriented; the end-emitting portion of the fiber can placed in direct proximity to the task. These systems are particularly useful for very detailed tasks that require high illumination levels. End-emitting systems are energy-efficient alternatives to using high levels of general illumination provided by ceiling integrated fluorescence.
Specific tasks that can efficiently employ fiber optic task lighting include:
Open laboratory environments that combine a general level of illumination using traditional ceiling integrated fluorescents with task lighting can use fiber optic systems efficiently to provide the task lighting. This lighting approach provides a low level of ambient illuminance over the entire space using an indirect lighting system with fixtures in a uniform grid; these fixtures are suspended from the ceiling and direct light up toward the ceiling, which evenly distributes the light down toward the task. Target illuminance would be between 30-50 foot-candles (considerably lower than the conventional 75-100 foot-candles one would encounter in a typical 2 ft. x 4 ft. lens troffer layout). This indirect approach provides lighting for general functions, including occupant circulation, and provides a glare-free environment for visual display terminal (VDT) applications. At individual and multi-task areas, a series of fiber optic illuminators can be mounted onto benches to provide individual task illumination.
2) Continuous-emitting – this system relies on a fiber that emits light continuously along its length in an isotropic or a directional pattern. An optical interruption to the total internal reflection process on the fiber optic surface allows for light scattering and then for emission along the length the fiber. Continuous-emitting fiber optic lighting systems will see greatly increased use in specialized laboratory spaces that require remote light sources applications. Continuous fiber optic systems allow for a narrow diameter fiber to be placed in a room as an extended light source, which can act just like a continuous row of fluorescent lamps placed end to end. Continuous-emitting systems are well suited to lighting larger areas in laboratory spaces, particularly for tasks that are long and linear in nature.
3) Series of discrete emitters – this system uses fibers that have small surfaces positioned along a length, emitting light at regular intervals. Specialized surfaces are positioned at regular intervals to interrupt the total internal reflection process, allowing for light to be emitted at that point along the fiber.
