Optical fiber module consists of core and a clad. The laser light and/or pulsed light (optical signal) travel through the core. In order to confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding.

For practical use, the clad is coated with various layers (jackets), trasforming optical fiber module to the optical fiber cable. Jackets are selected depending on the intended end-usage; strengthen the fiber (but do not contribute to its optical wave guide properties).

>> Core / Clad / Covering layer

Optical fibers are divided into two categories, according to the number of modes, types of ray trajectory, transimitted in the core.

• Single-mode fiber (SF)

  SF fibers have small-diameter core and are frequently used in communication systems.

>> Single-mode fiber

• Multi-mode fiber (MF)

  MF fibers are frequently used in LAN cables. In MF fiber, the velocity of light varies depending on reflectance mode.

>> Multi-mode fiber

Characteristics of optical fiber

• Long-distance transmission
• Low losses
• Chemical stability (made of glass)
• Insensitivity to interfarence from electromagnetic wave