pciaccio Wed, 06/20/2007 - 07:54
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A single mode fiber has an optical core diameter of 8um (micro meters; 10^-6 meters). Multimode fiber can be either 50um or 62.5um. The Single mode fiber is typically used by carriers and can run longer distances without the need of a repeater and use a laser to xmit onto the fiber (typically these are Yellow in color).These are more expensive then Multimode fiber. Multimode fibers are typically used for all other applications and mostly use a LED xmitter but can use a laser xmitter (typically these are Orange in color, I've seen some in Blue)....

Jagdeep Gambhir Wed, 06/20/2007 - 07:59
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Hi Carl,

Multimode is a type of optical fiber mostly used for communication over shorter distances, such as within a building. It can carry 1 Gbit/s for typical building distances; the actual maximum data rate (given the right electronics) depends upon the distance.

Multi-mode fiber has a higher light-gathering capacity than single-mode optical fiber, making splicing less difficult, but its limit on speed ? distance is lower.

Single-mode optical fiber (SMF) is an optical fiber designed to carry only a single ray of light (mode). This ray of light often contains a variety of different wavelengths. Although the ray travels parallel to the length of the fiber, it is often called the transverse mode since its electromagnetic vibrations occur perpendicular (transverse) to the length of the fiber.

Hope that helps !



chrihussey Wed, 06/20/2007 - 08:09
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Multimode fiber has a larger diameter core or simply put is fatter than singlemode fiber and to some extent is not as clean or pure and costs less.

Multimode generally works fine in campus environments but if longer distances are needed then single mode is used.

Different light wavelengths travel can cleanly travel different distances down multimode and single mode fiber.

If it helps, the link below highlights the standard distances of the different Cisco GBICs across multi and singrl mode fibers.



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