subject: The Differences Between Radiations [print this page] Most optical fibers used transmit light in the near infrared light at wavelengths of 800-1600 nm. The silica glasses used in most fibers are transparent at these wavelengths. Plastic fibers transmit best at visible wavelengths, but they are not as transparent as those wavelengths as glass fibers are in the infrared. Special fibers, which are currently in development, are made of materials other than silica and can transmit light at longer infrared wavelengths. Some special grade silica can transmit some near ultraviolet light.
The speed of light in a material is always slower than in vacuum, so the refractive index is greater than one in the optical part of the spectrum. Although light travels in straight lines through optical materials, light is bent at the surface. This happens as the refractive index changes as it moves from one medium to another. When the angle of incidence exceeds a critical value, where the site of the angle equals one (Snell's Law) the light will undergo total internal reflection and be bounced back into the glass.
The fundamental difference between a fiber optic communication system and other types is that signals are transmitted as light. Conventional electronic communication relies on electrons passing through cables. Microwave communication relies on microwaves travelling through open space. High transmission capacity and long transmission distance are two major advantages of fiber optics compared with metal cables. However, different factors can dictate the choice of fiber for other applications.
When the angle of incidence exceeds a critical value, where the site of the angle equals one (Snell's Law) the light will undergo total internal reflection and be bounced back into the glass.
