is broadly defined to include any use of sunlight to illuminate the interior of a structure.
Hybrid solar lighting
(HSL) systems combine the use of sunlight with artificial light for interior illumination by piping sunlight through fiber optic cable bundles to provide sunlight into rooms without windows or skylights, and by supplementing this natural light with artificial light as required. The bundles are led from exterior/rooftop optical light collectors through small openings or cable ducts and carry the light to where it is needed. The optical fibers end in hybrid luminaires where the sunlight is joined with electric light, either on demand or to automatically maintain a constant light level even as the available sunlight decreases.
are lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. Compared to conventional bulky lenses, the Fresnel lens is much thinner, larger, and flatter. It reduces the amount of material required compared to a conventional spherical lens by dividing the lens into a set of concentric annular sections known as “Fresnel zones.”
Plastic Optical Fibers
are optical fibers made out of plastic. Traditionally PMMA (acrylic) is the core material, and fluorinated polymers are the cladding material. Similar to traditional glass fiber, POF transmits light (or data) through the core of the fiber but the core size of POF is in some cases 100 times larger than glass fiber.
POF has been called the “consumer” optical fiber because the fiber and associated optical links, connectors, and installation are all inexpensive. Due to its attenuation and distortion characteristics POF is commonly used for low-speed, short-distance (up to 100 meters) applications in digital home appliances, home and industrial networks or for transmission of light in HSL applications.