Fiber Optic Wiki

Ethernet crossover cable

December 5, 2011

An Ethernet crossover cable is a type of Ethernet cable used to connect computing devices together directly. Normal straight through or patch cables were used to connect from a host network interface controller (a computer or similar device) to a network switch, hub or router.

Overview of the 10BASE-T and 100BASE-TX Ethernet

December 5, 2011

The 10BASE-T and 100BASE-TX Ethernet standards use one wire pair for transmission in each direction. By convention, one wire of the pair is designated "+" and the other "-". Following traditional telephone terminology, the + signal from each pair connects to the tip conductor, and the - signal is connected to the ring conductor. This requires that the transmit pair of each device be connected to the receive pair of the device on the other end.

Telephone Networks

December 3, 2011

Telephone networks were the first major users of fiber optics. Fiber optic links were used to replace copper or digital radio links between telephone switches, beginning with long distance links, called long lines, where fiber's distance and bandwidth capabilities made fiber significantly more cost effective. Telcos use fiber to connect all their central offices and long distance switches because it has thousands of times the bandwidth of copper wire and can carry signals hundreds of times further before needing a repeater - making the cost of a phone connection over fiber only a few percent of the cost of the same connection on copper. They even use fiber to connect cell phone towers to save limited radio spectrum.

The Internet

December 3, 2011

The Internet has always been based on a fiber optic backbone. It started as part of the telephone network which was then primarily voice but has become the largest communications network as data traffic has outgrown voice traffic. Now the telcos are moving their voice communications to Internet protocol (IP) for lower costs.

The development of highly linear

December 3, 2011

The development of highly linear distributed feedback (DFB) lasers allowed CATV systems to be converted to analog optical systems. CATV companies "overbuild" with fiber. They connect their headends with fiber and then take fiber into the neighborhood. They lash the fiber cable onto the aerial "hardline" coax used for the rest of the network or pull it in the same conduit underground. The fiber allows them to break their network into smaller service areas, typically fewer than 4 amplifiers deep, that prevent large numbers of customers from being affected in an outage, making their network more reliable and easier to troubleshoot, providing better service and customer relations.

Premises Networks

December 3, 2011

Premises networks, mostly computer LANs (local area networks) use fiber optics primarily in the backbone but increasingly to the desk and to connect wireless access points. The LAN backbone often needs longer distances than copper cable (Cat 5/5e/6/6A) can provide and of course, the fiber offers higher bandwidth for future expansion. Fiber's ability to handle network upgrades meant that one fiber type outlived nine generations of copper cables in LANs. A new fiber type (OM3) offers future potential for upgrades while copper continues to struggle with network speed increases.

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