– plenum cable is coated with a fire-retardant

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Plenum cable is coated with a fire-retardant coating (usually Teflon) so that in case of a fire it does not give off toxic gasses and smoke as it burns.
© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 630Fiber MediaFiber-optic cabling uses either glass or plastic fibers to guide light impulses from source to destination. –The bits are encoded on the fiber as light impulses. –Optical fiber cabling is capable of very large raw data bandwidth rates. Fiber Compared to Copper Cabling–The fibers media is immune to electromagnetic interference and will not conduct unwanted electrical currents. Optical fibers are thin and have relatively low signal loss, they can be operated at much greater lengths than copper media. •In most enterprise environments, optical fiber is primarily used as backbone cabling for high-traffic connections and for the interconnection of buildings in multi-building campuses. –Some optical fiber Physical layer specifications allow lengths that can reach multiple kilometers.
© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 631Fiber MediaOptical fiber media implementation issues include:More expensive (usually) than copper media over the same distance (but for a higher capacity)Different skills and equipment required to terminate and splice the cable infrastructureMore careful handling than copper media
© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 632Fiber Media: Cable ConstructionOptical fiber cables consist of a PVC jacket and a series of strengthening materials that surround the optical fiber and its cladding. –The cladding surrounds the actual glass or plastic fiber and is designed to prevent light loss from the fiber. Because light can only travel in one direction over optical fiber, two fibers are required to support full duplex operation. –Fiber-optic patch cables bundle together two optical fiber cables and terminate them with a pair of standard single fiber connectors. –Some fiber connectors accept both the transmitting and receiving fibers in a single connector.
© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 633Generating and Detecting the Optical SignalEither lasers or LEDs generate the light pulses that are used to represent the transmitted data on the media. –Electronic semi-conductor devices called photodiodes detect the light pulses and convert them to voltages that can then be reconstructed into data frames. –The laser light transmitted over fiber-optic cabling can damage the human eye. Avoid looking into the end of fiber.Fiber optic cables can be broadly classified into two types:–Single-mode optical fiber •Carries a single ray of light, usually emitted from a laser.

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