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micrometer fiber is 8 microns in diameter (almost an eighth of that of the Multi-Mode fiber) surrounded by a second outer clad. This clad can pass a light signal, so for this reason the fiber is referred to as 9 by 125 micrometer fiber.
FIGURE 13: Differences between Multi-Mode and Single-Mode Cable
7.2.2 Single mode fiber - Less attenuation per unit distance
The difference between multi-mode and single mode cable can be best described as follows:
With multi-mode fiber the index of refraction at the surface between the core and the cladding is such that there is total internal reflection of the light being transmitted down the core. Picture this by imagining that the clad is a tube whose interior surface is polished so smooth, it is like a mirror. Light shinning at one end of the tube will either travel straight down the tube or will travel down the tube by reflecting of the inner mirrored surface.
Single mode fiber can be described as an elongated lens that is continuously focusing the light into the centre of the fiber. Using these two analogies it can be imagined that in the single mode fiber more light travels through far less fiber medium resulting in far less attenuation per unit distance than it does in multi-mode fiber. As a result, for a given wavelength of light, single mode fiber typically has less attenuation per unit distance than multi-mode fiber.
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