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Transcript
24 Wired Transmission 24 Wired Transmission • This is about the method used to actually transmit or send data • That means actual wires or cables • You need to know three types • And the advantages/disadvantages • You might think wires are boring • But imagine life without Sky TV, the web and computer networks… 24 Wired Transmission UTP Cable Co-axial Fibre Optic 24 Wired Transmission • When it comes to cabling, you might think ‘who cares’ ? • But networks are hugely important today • So designers take care to pick the right cable to build networks • Key issues are cost and speed, meaning how much data the cable can carry • The goal is to reduce latency • That’s the delay in between sending and receiving data 24 Wired Transmission STP Cable Network Co-axialTV Digital Backbone Fibre Optic Backgrounder – Cables & Digital Data 24 Wired Transmission • Information such as computer data and telephone calls can be converted into electrical signals • These can be carried through wires that conduct electricity, such as copper cables • But the info can also be converted into light signals and transmitted by optical fibre • Let’s have a quick look at how that works… Backgrounder – Data Means Bits 24 Wired Transmission Remember that ‘digital’ data means 1s & 0s… Binary Bit is a 0 or a 1 Byte is 8 bits 01100001 Backgrounder – Electric Signals 24 Wired Transmission That digital data can be shown as a ‘square’ wave, like on & off… 0 1 1 0 0 0 0 1 And those 1s and 0s could be high & low voltage on a wire… But electric signals must have no interference to get clean 1s & 0s 24 Wired Transmission UTP • UTP is the cable used for for most LANs, like our network in school • It’s called Unshielded Twisted Pair • Inside are several pairs of copper wire • They’re twisted to stop electrical interference • UTP cable is popular for LANs because it is cheap and can carry lots of data • There’s also Shielded Twisted Pair (STP)… 24 Wired Transmission UTP Unshielded STP Shielded 24 Wired Transmission Co-Axial • You’ll find ‘coax’ round the back of at your satellite TV box • It has two copper conductors separated by an insulator • That enables it to work at higher data rates than twisted pair • It can be used for networks but costs more than UTP and is harder to install because it’s not as flexible 24 Wired Transmission Fibre Optic • Strands of glass as thin as hair that carry data as light • Lots of fibres are bundled together to form cables • Cheaper than traditional copper telephone wire • T1 lines give local connection • T3 lines form Internet backbone 24 Wired Transmission 24 Wired Transmission SUBMARINE 24 Wired CABLE MAP Transmission Backgrounder – Electrical Interference 24 Wired Transmission Optical signals can be transmitted so far due to how light travels… Backgrounder – Optical Data 24 Wired Transmission • A laser at one end of the pipe switches on and off to send each bit. • Modern fiber systems with a single laser can transmit billions of bits per second -- the laser can turn on and off several billions of times per second. • The newest systems use multiple lasers with different colors to fit multiple signals into the same fiber. 24 Wired Transmission STP Cable Network Co-axial Digital TV Fibre Optic Backbone 24 Wired Transmission 24 Wired Transmission