eFunda: Fiber Optics Introduction
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Overview
Fiber Optics is a datacommunications technology that has revolutionized data transfer. The advantages of light as a data transmission medium were apparent even in the time of Alexander Graham Bell. A suitable conduit had to be found, and this came to fruition in the form of the optical fiber.

In principal, fiber optics serves the same purpose as copper wire by moving information from one place to another. However, the transmission medium is light, and that light is carried within a hair-thin optical fiber via the process of total internal reflection.

Advantages of fiber optics include:

  1. High data transmission rates and bandwidth.
  2. Low losses.
  3. Small cable size and weight.
  4. Immunity to EMI (both with respect to susceptibility and emissions).
  5. Safety due to lack of sparks.
  6. Data security.
With the advent of the internet, the need for fiber optics has become especially acute. The current boom in fiber optics companies is a direct result of the high bandwidth required by internet data, especially graphical data. The list of applications continues to grow.
Internal Reflection
The following figure illustrates the transmission of light within a fiber via total internal reflection. As long as the incident angle is less than the critical angle, the light will be totally reflected without attenuation.

Fiber Bending Concerns
The modern optical fiber is extremely thin and light. Although seemingly fragile, properly-clad optical fiber is remarkably robust. Bending radius, however, is an issue. The following illustration shows how excessive macro or micro-bending can cause signal attenuation.

To prevent excessive fiber bending, specialized cable pullers must be used for routing fiber cable within a building. A simplex puller is shown below:

Connector Basics
Fiber optic connectors are a critical part of a fiber communication system since they allow plug-and-play and rerouting of signals, similar to a wire network. However, fiber optic connectors can be difficult to implement since the fiber is so thin and fragile. The following figure illustrates the configuration of an FSMA connector, one of the earlier connectors used from the late seventies.

The lowest attenuation material for fiber optic cable is quartz, but for less-expensive applications plastic fiber can be used. The following illustrations show typical plastic fiber optic connectors.

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