Fiber Optic
Fibre optic cabling consists of a centre glass core surrounded by several layers of protective materials (See fig. 5). It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between
Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is
The centre core of fiber cables is made from glass or plastic fibers (see fig). A plastic coating then cushions the fiber centre, and Kevlar fibers help to strengthen the cables and prevent breakage. The outer insulating jacket made of Teflon or PVC.
Fiber optic cable
There are two common types of fiber cables — single mode and multimode. Multimode cable has a larger diameter; however, both cables provide high bandwidth at high speeds. Single mode can provide more distance, but it is more expensive.
Ethernet Cable Summary
Specification Cable Type
10BaseT Unshielded Twisted Pair
10Base2 Thin Coaxial
10Base5 Thick Coaxial
100BaseT Unshielded Twisted Pair
100BaseFX Fiber Optic
100BaseBX Single mode Fiber
100BaseSX Multimode Fiber
1000BaseT Unshielded Twisted Pair
1000BaseFX Fiber Optic
1000BaseBX Single mode Fiber
1000BaseSX Multimode Fiber
Wireless LANs
More and more networks are operating without cables, in the wireless mode. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite.
Wireless networks are great for allowing laptop computers or remote computers to connect to the LAN. Wireless networks are also beneficial in older buildings where it may be difficult or impossible to install cables.
The two most common types of infrared communications used in schools are line-of-sight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network. Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks.
Wireless standards and speeds
The Wi-Fi Alliance is a global, non-profit organization that helps to ensure standards and interoperability for wireless networks, and wireless networks are often referred to as Wi-Fi (Wireless Fidelity). The original Wi-Fi standard (IEEE 802.11) was adopted in 1997. Since then many variations have emerged (and will continue to emerge). Wi-Fi networks use the Ethernet protocol.
Standard Max Speed Typical Range
802.11a 54 Mbps 150 feet
802.11b 11 Mbps 300 feet
802.11g 54 Mbps 300 feet
Advantages of wireless networks:
Wireless Lan
Mobility – With a laptop computer or mobile device, access can be available throughout a school, at the mall, on an airplane, etc. More and more businesses are also offering free Wi-Fi access.
Fast setup – If your computer has a wireless adapter, locating a wireless network can be as simple as clicking “Connect to a Network” — in some cases, you will connect automatically to networks within range.
Cost – Setting up a wireless network can be much more cost effective than buying and installing cables.
Expandability – Adding new computers to a wireless network is as easy as turning the computer on (as long as you do not exceed the maximum number of devices).
Disadvantages of wireless networks:
Security
Security – Wireless networks are much more susceptible to unauthorized use. If you set up a wireless network, be sure to include maximum security. You should always enable WEP (Wired Equivalent Privacy) or WPA (Wi-Fi Protected Access), which will improve security and help to prevent virtual intruders and freeloaders.
Interference – Because wireless networks use radio signals and similar techniques for transmission, they are susceptible to interference from lights and electronic devices.
Inconsistent connections – How many times have you hears “Wait a minute, I just lost my connection?” Because of the interference caused by electrical devices and/or items blocking the path of transmission, wireless connections are not nearly as stable as those through a dedicated cable.
Power consumption – The wireless transmitter in a laptop requires a significant amount of power; therefore, the battery life of laptops can be adversely impacted. If you are planning a laptop project in your classroom, be sure to have power plugs and/or additional batteries available.
Speed – The transmission speed of wireless networks is improving; however, faster options (such as gigabit Ethernet) are available via cables. In addition, if set up a wireless network at home, and you are connecting to the Internet via a DSL modem (at perhaps 3 Mbps), your wireless access to the Internet will have a maximum of 3 Mbps connection speed.
Scale
Networks are often classified as local area network (LAN), wide area network (WAN), metropolitan area network (MAN), personal area network (PAN), virtual private network (VPN), campus area network (CAN), storage area network (SAN), and others, depending on their scale, scope and purpose. Usage, trust level, and access right often differ between these types of network. For example, LANs tend to be designed for internal use by an organization’s internal systems and employees in individual physical locations (such as a building), while WANs may connect physically separate parts of an organization and may
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