Optical fiber is typically defined by its size, attenuation and bandwidth and it works by sending signal down hair-thin strands of glass or plastic fiber. When choosing fiber it is important to consider how it will be used. Is it device to device? Does it need to be run horizontal/intra-office (single floor but multiple rooms), rise/intrabuilding (run between floors), aerial (strung from utility poles and self-supporting), direct burial, duct, submarine or inside-outside? Determining the environment in which the fiber will be installed will help simplify the decision-making process.

The two types of fiber most commonly used are singlemode and multimode fibers. Both multimode and singlemode fibers are slightly larger than a human hair but the way light travels through the two types of fiber varies significantly. Light travels through multimode fiber in many rays or modes. Multimode fiber has a larger core and it is typically used for slower area networks. Singlemode fiber, on the other hand, has a smaller core which allows light to travel in only one ray or mode. It is used for telephones and CATV.

Singlemode fiber is usually considered to be one size and type (with the exception of specialty singlemode fibers). Multimode, in comparison, originally came in several sizes for use in various networks or sources but has since been standardized to a single size (62.5 core fiber).

An important thing to keep in mind is that fibers cannot be mixed and/or matched. Mixing singlemode and multimode fiber can cause significant loss in power (up to 99%).

Some of the features of single-mode fiber versus multi-mode fiber:

Single-Mode FiberMulti-Mode Fiber
BandwidthVirtually UnlimitedLess
Signal QualityExcellent Long DistanceExcellent Short Distance
Primary AttenuationChromatic DispersionModal Dispersion
Fiber TypesStep Index and Dispersion ShiftedStep Graded Index
Typical ApplicationsAlmost AnythingAnalog Video, Short Range Communications

If you have any further questions regarding the use of single-mode and multi-mode fiber, please don’t hesitate to ask!

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