Waterproof Fiber Cable

1-144 cores GYTY53 Double Jacket Direct Buried Optical Fiber Cable

Learn more about Fiber Optic Cable:

Fiber types. The left of the drawing shows the core/cladding diameters. The right part of the drawing shows the index profile of the fiber. The index profile shows the relative index of refraction of the material used in making the fiber.

Total Internal Reflection

The index of refraction of glass or any optical material is a measure of the speed of light in the material and changes in index of refraction are what causes light to bend - as shown in this photo of a plastic rod in a pond:

refraction

Beyond a certain angle, the refraction will cause light to be reflected from the surface. Optical fiber uses this reflection to "trap" fiber in the core of the fiber by choosing core and cladding materials with the proper index of refraction that will cause all the light to be reflected if the angle of the light is below a certain angle. We call that "total internal reflection."

Total Internal Reflection In Optical Fiber

There is an angle that for any given fiber defines total internal reflection. At higher angles a ray of light will be refracted but not enough so it is lost in the cladding of the fiber. Below that angle, it will be reflected back into the core of the fiber and transmitted to the end of the fiber. The angle of total internal reflection defines the "numerical aperture" (NA) of the fiber, a standard fiber specification.

Step Index Multimode Fiber

Step index multimode fiber was the first fiber design. The core of step index multimode fiber is made completely of one type of optical material and the cladding is another type with different optical characteristics. It has higher attenuation and is too slow for many uses, due to the dispersion caused by the different path lengths of the various modes traveling in the core. Step index fiber is not widely used - only POF and PCS/HCS (plastic or hard clad silica, plastic cladding on a glass core) use a step index design today. POF is mainly used for consumer audio and TV links.