Networking Guide : Physical Media - Fiber Optic

fiber optic

Picture: Fiber optic structure

Fiber Optic (optical fiber) is a thin glass or plastic strand in the core which is surrounded by a cladding and a protective coat and is used to carry information in optical (light) pulses. Because in fiber optic, information is transmitted in optical pulses instead of electrical signals, fiber optic is not affected by EMI (electromagnetic interference) and RFI (radio frequency interference). Moreover, fiber optic has very large bandwidth which is limited only by the equipment that lights the fiber (i.e. SDH/SONET, ATM, DWDM). But fiber optic is more expensive than twisted pair, coax and radio.

single-mode multimode

Picture: single-mode fiber (left) and multimode fiber (right)

Fiber optic is often classified into single-mode and multimode. In a single-mode fiber, light travels in one path (mode). In a multimode fiber, light travels in multiple paths (multimode). Single mode fiber can reach longer distance than multimode fiber, so it is mostly used for MAN or WAN. While multimode fiber is suitable for implementing high speed LAN.

Because of its reliability and wider bandwidth, fiber optic is often used in backbone networks where cables run in ducts and in broadband networks that deliver bandwidth intensive applications, such as HDTV, video streaming, video conferencing and Video on Demand.

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