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Fiber Optic Lighting Systems


Recently, a new mode of lighting has been introduced for interior space lighting which replaces multiple electrically powered lights with a single, high efficiency, long-life light source and a collection of light guides which pipe the light to the desired area. The light source may be of various types; currently, metal-halide lamps and the newly developed RF-pumped sulfur lamps, are the most popular sources. It is also possible to use solar concentrators during daylight hours to pump the optical fibers directly from sunlight - saving electricity.

Piped Lighting Systems

The light may be carried to the destination in a number of ways. In the Air & Space Museum a 280-foot transparent light pipe covered with a special film is used. For the Artemis Project's purposes, a more suitable method would be to use low-cost, low-weight plastic fibers, such as those made by the Lumenyt Corporation . With such fibers, bundles totaling up to 60 fibers are end-illuminated with a high-intensity light source. The end of each fiber is then simply aimed towards the surface of the area to be illuminated, or perhaps towards the ceiling if a more diffuse light is desired.

Figure 1
Figure 1 - Fiber Light Sources

There are several advantages to piped lighting over more conventional lighting schemes: 

  1. The smaller number of higher-reliability, albeit more expensive, light sources results in a much longer MTBF (Mean Time Between Failures).  
  2. The system is considerably more reliable and easier to maintain, since the distribution fibers themselves have indefinite lifetimes and all maintenance action is concentrated in one location.  
  3. For reliability and fail-safe purposes, a number of central light sources would be used and placed in several separated locations.  
  4. The illumination system should be less massive than a system using many separate bulbs and copper wiring.  
  5. Safety is enhanced, since the fibers carry no electrical current.  
  6. During the day, the fibers can be pumped directly from solar concentrators, using no electricity at maximum efficiency. Switching between light sources involves a simple mechanical fiber-optic switch, resembling a train track switch.


RF-Pumped Sulfur Bulbs

Microwave-pumped sulfur bulbs are a relatively new, although proven, technology that offers many advantages for illuminating lunar bases. These bulbs are already being used for applications such as the Smithsonian Air & Space Museum and the DOE headquarters in Washington DC. Sulfur bulbs are somewhat more complicated than incandecent bulbs, since they use a microwave RF source to drive the bulb and require physical rotation of the bulb, but their efficiency is very high, they do not dim with age, and their lifetimes are considerably longer - over 10,000 hours, primarily limited by the magnetron used to excite the bulb. The following table compares RF-sulfur bulbs with several other commercial lighting sources.

Comparison of Bulb Characteristics. Courtesy of Fusion Lighting Inc.
Bulb TypeMTBF, HoursOutput, Lumens/WattComments
RF sulfur60,00080-100Cooler than Metal Halide; Magnetron replacement at 15,000 hours; needs EMI shielding; very high output intensities available
Metal Halide20,00080-105Very hot running; high output intensities available
Fluorescent10,000-20,00080-90Very cool running; not available for high output intensities
Incandescent1,000-5,00017-18Hot running, most output is in IR


Example Calculation for Greenhouse

One primary application for this lighting system will be to provide illumination for the agricultural greenhouse providing food for the settlement. See the essay on modular greenhouses in Section as an example of an installation using this lighting system.

As an example calculation, let's suppose a 100-square-meter greenhouse tray. (This is for calculation purposes only, the system is easily scalable.) Let us then suppose that the average cable run for a light-pipe system in a dome, toroid, or cylinder is 25 meters.

Figure 2
Figure 2 - Fresnel Solar Concentrator


The advantages to centrally-lit light-pipe illumination system are many. The fibers are light-weight and safe in any atmospheric or environmental condition. They are also highly reliable and difficult to damage. Fixturing is minimal at the illumination site and may be as simple as holding the fiber end in a clip and aiming it at the ceiling.

During the night, the light is obtained from a few, highly reliable, high-efficiency sources that are easily maintained. RF-pumped sulfur bulbs are recommended due to their high efficiency and reliability, as well as their low thermal output.

During the day, no electrical power is required to run the system, and all photovoltaic systems may be used for other purposes (e.g., charging storage systems for night use). The only electro-mechanical parts are the solar concentrators, which would use simple single-axis drive motors.


1. Remote Source Lighting International, Inc32961 Calle PerfectoSan Juan Capistrano, CA 92675USA714-248-0141714-248-0142

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