Introduction
- In 1870, J.Tyndall, a British physicist demonstrated in front of British Royal Society that light propagates along the center line of bent water stream by investigating the light stream flashed from the top of the water tank travelling through the water stream ejected from a hole of water tamk. Actual light route is mot bent, but the light travels zigzag way repeating total internal reflections many times along the inside of the water stream.
It is optical fiber to utilize very fine optical fiber material instead of water stream.
Plastic optical fiber was developed by Dupont Company in 1963,and its techmology and patent, dtc. were sold to Mitsubish Rayon at the end of 1980. Plastec optical fiber was developed not only for lighting but also for communication purpose.
Optical fiber utilizes total internal reflection due to the critical angle made using difference between reflective indexes of 2 materials (Core and Clad) which have different reflective indexes each other.
Structure of optical fiber
- Optcal fiber consists of Core and Cladding.
Core conveys light signals, and cladding has a roll to confine the light signals within the core. 
Manufacturing process of optical fiber
- There are 3 main processing steps in making optical fiber.
- 1 step of manufacture of optical fiber is to manufacture high degree of a pure glass preform. If glass preform is once made, then optical fiber is drawn from the glass preform, and lastly geomeric structure and optical characteristics of the optical fiber are inspected and tested.
- 1.Manufacture of glass prefrom
Glass perorm is manufactured using various ratio of chemical materials such as germanium dioxide in order to make different refractive indexes of silicon oxide of basic components in the core area. In general,single mode optical fiber contains small amount of germanium dioxide and multimode optical fiber contains a lot of germanium dioxide in order to get a higher refractive index. There are many ways to manufacture preform, distribution of internal reflective indexes of made preform are measured with PRIP analyzer comparing with designed specifications. The Quartz glass tube made through such process vecomes cladding area of preform. The preform of desired diameter is completed vy expanding the diameter of preform by covering a 2 quartz glass tube as a cladding area. -
2. Optical fiber draw
If preform is heated in the heater until the temperature reaches to 1900℃ then tip of preform starts to become soft. The prefotm falls dowm due to gravity in the cortse of time passing them optical fiber becomes thinner. After optical fiber of diameter 125um is made as above, buffer is covered on it to make optical fiber of diameter 250um. Drawn optical fiber is wound on a small spool in a required length and its tensile strength is tested by passing through the ooad applied wheel. 
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3. Geometric structure and characteristics inspection
Quality of optical fiber is strictly controlled through structural characteristics test of cladding, buffer, core and optical characteristic test of loss, bandwidth, etc, and reliability test.
Feature of optical fiber lighting device
| Cold lighting : Optical fiber conveys light only, therefore heat is not generated in the optical fiber itself, there occurs no deformation and decolorization to the subject by heat, and it is not affected by temperature and humidity, etc. of surrounding environment. |
| It is possible to use visual light rays only or specific bandwidth light only by equipping with filters in the light source device. |
| It is well harmonized with environment differently from general lighting such as incandescent light, fluorescent light, neon light, therefore it can display light creating neat and refresh feeling. It conveys light only and it is not related to elecatrical risks such as short circuit, discharge, etc. therefore it is specifically good for outdoor lighting and underwater lighting. |
| It is different from general lighting using glass tubes, and it does not have a risk of brekage, and it has escellent flexibility therefore it can display free shapes, and it can light narrow and small and curved dangerous olaces. |
| General lighting may cause time and space limitation and dangerous for replacement of lamp, but optical fiber lighting is convenient to replace easily the lamp only located in the light source device installed at convenient places. |
| It can save electricity cost and has excellent durability. |
| It has various color changes and display methods. |
| It can provide even high brightness lighting. |
| It has various lighting methods such as dot lighting, gace lighting, line lighting, etc. |
