Fiber-Optic Overview



Optical fiber definition

Fiber-optic communications is based on the principle that light in a glass medium can carry more information over longer distances than electrical signals can carry in a copper or coaxial medium. Today's glass fiber is able to transmit digitized light signals well beyond 100 km (60 miles) without amplification. With few transmission losses, low interference, and high bandwidth potential, optical fiber is an almost ideal transmission medium.

Single-mode and multimode fibers

There are two general categories of optical fiber: single-mode and multimode. Multimode fiber was the first type of fiber to be commercialized. It has a much larger core than single-mode fiber, allowing hundreds of modes of light to propagate through the fiber simultaneously. Additionally, the larger core diameter of multimode fiber facilitates the use of lower-cost optical transmitters (such as light emitting diodes [LED's]).

Single-mode fiber, on the other hand, has a much smaller core that allows only one mode of light at a time to propagate through the core. Single-mode fibers are designed to maintain spatial and spectral integrity of each optical signal over longer distances, allowing more information to be transmitted.

Single-mode fiber is typically used for longer-distance and higher-bandwidth applications. Multimode fiber is used primarily in systems with short transmission distances (under 2 km), such as connecting buildings in a campus environment.

Fiber-optic versus copper

Fiber offers a number of advantages over copper. Its information carrying capacity far surpasses that of copper while providing greater security. Its low loss characteristics allow for longer cable runs without the need for repeaters. Immunity to radio frequency interference (RFI) and electromagnetic interference (EMI) allows fiber to be isolated from its environment, resulting in error-free transmission. Fiber-optic cable is small and lightweight compared to copper solutions.

* Information provided by Corning Incorporated