Transmission Media: Overview and Design Factors

1. COMP 421 /CMPET 401 COMMUNICATIONS and NETWORKING CLASS 5 (4B)

2. TRANSMISSION MEDIA

3. Overview • Guided - wire • Unguided - wireless • Characteristics and quality determined by medium and signal • For guided, the medium is more important • For unguided, the bandwidth produced by the antenna is more important • Key concerns are data rate and distance

4. Design Factors • Bandwidth • Higher bandwidth gives higher data rate • Transmission impairments • Attenuation • Interference • Number of receivers • Major factor in guided media • More receivers (multi-point) introduce more attenuation

5. Electromagnetic Spectrum

6. Guided Transmission Media • The transmission capacity depends on the distance and on whether the medium is point-to-point or multi-point Medium Freq Typical Typical Repeater Range Atten. Delay Spacing • Twisted Pair 0 - 3.5KHz 0.2dB/km 50us/km 2km • Twisted Pair 0 - 1.0MHz 3.0dB/km 5 us/km 2km • Coaxial cable 0 - 500MHz 7.0dB/km 4 us/km 1-9km • Optical fiber • Multi-mode 180-370THz 0.5dB/km 5 us/km 2km • Single Mode180-370THz 0.2dB/km 5 us/km 40km

7. Twisted Pair • Consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs • Often used at customer facilities and also over distances to carry voice as well as data communications • Low frequency transmission medium

8. Twisted Pair - Applications • Most common medium • Telephone network • Between house and local exchange (subscriber loop) • Within buildings • To private branch exchange (PBX) • For local area networks (LAN) • 10Mbps or 100Mbps

9. Twisted Pair - Pros and Cons • Cheap • Easy to work with • Low data rate • Short range

10. Twisted Pair - Transmission Characteristics • Analog • Amplifiers every 5km to 6km • Digital • Use either analog or digital signals • repeater every 2km or 3km • Limited distance • Limited bandwidth (1MHz) • Limited data rate (100MHz) using different modulation & signaling techniques • Susceptible to interference and noise

11. Unshielded and Shielded TP • Unshielded Twisted Pair (UTP) • Ordinary telephone wire • Cheapest • Easiest to install • Suffers from external electromagnetic interference (EM) • Shielded Twisted Pair (STP) • the pair is wrapped with metallic foil or braid to insulate the pair from electromagnetic interference • More expensive • Harder to handle (thick, heavy)

12. UTP Categories • Cat 3 • up to 16MHz • Voice grade found in most offices • Twist length of 7.5 cm to 10 cm • Cat 4 (least common) • up to 20 MHz • Cat 5 • up to 100MHz • Commonly pre-installed in new office buildings • Twist length 0.6 cm to 0.85 cm

13. Category 5E and 6 Today, cables and related components are available in more grade categories than the industry standards specify. You can choose from Cat 5, Cat 5e, Cat 5e+, Cat 6 and yes, even Cat 6+. While there is plenty of hype and confusion surrounding these implied categories

14. Cat 6 more than doubles the bandwidth of Cat 5e, from 100 MHz to 250 MHz, supporting future emerging applications Improved EMC performance to reject outside noise from TVs, wireless, and other adjacent applications. Full backwards compatibility to support all legacy applications Simpler and less costly installations, due to reduction in electronics needed for echo and NEXT (Near End Cross Talk) cancellation. CAT 6 Features

15. Equations for CAT 6 Parameters Attenuation (dB) = 1.991*sqrt(f) + 0.01785*f + 0.21/sqrt(f) pr-pr NEXT (dB) = -20log( 10^( -0.05(74.3-15log(f)) ) + 2*10^( -0.05(94.0-20log(f)) ) ) PSNEXT (dB) = -20log( 10^( -0.05(72.3-15log(f)) ) + 2*10^( -0.05(90.0-20log(f)) ) ) pr-pr FEXT (dB) = -20log( 10^( -0.05(67.8-20log(f)) ) + 4*10^( -0.05(83.1-20log(f)) ) ) PSFEXT (dB) = -20log( 10^( -0.05(72.3-20log(f)) ) + 4*10^( -0.05(90.0-20log(f)) ) ) Return loss (dB) = 19 at 1-20 MHz; 19-10*log(f/20) at 20-250 MHz Phase Delay (ns) = 546 + 34/sqrt(f) Delay skew (ns) = 50 pr-pr PS pr-pr PS return phase delay freq atten NEXT NEXT ELFEXT ELFEXT loss delay skew (MHz) (dB) (dB) (dB) (dB) (dB) (dB) (ns) (ns) 100 21.7 39.9 37.1 23.2 20.2 12.0 549.4 50.0 250 36.0 33.1 30.2 17.2 14.2 8.0 548.2 50.0

16. The RJ 45 Connector To identify the RJ-45 cable type, hold the two ends of the cable next to each other so you can see the colored wires inside the ends ·Straight-through — the colored wires are in the same sequence at both ends of the cable. Crossover — the first (far left) colored wire at one end of the cable is the third colored wire at the other end of the cable

17. 8-Wire Jack(10BaseT Data Connections) 8-Wire Jacks(USOC RJ31X Through RJ37X) 6-Wire Jack(USOC - RJ14W) Understanding USOC & RJ

18. 8-Wire Jack(IBM Token Ring Connections) 8-Wire Jacks(USOC RJ41 Through RJ48)Also TIA 568B(TIA 568A Swaps Pairs 2 & 3) 6-Wire Jack Modified Jack(DEC MMJ) Understanding USOC & RJ

19. Twisted Pair Advantages • Inexpensive and readily available • Flexible and light weight • Easy to work with and install

20. Twisted Pair Disadvantages • Susceptibility to interference and noise • Attenuation problem • For analog, repeaters needed every 5-6km • For digital, repeaters needed every 2-3km • Relatively low bandwidth

21. LEVEL 5 CABLING PER Specification TSB-36 for UTP cable connections for LEVEL 5: - A terminal jack can be 90M (295ft) from the wiring closet. - A device can be 10M from a terminal jack at the users location. - There can be up to 6M of cross-connect patch cords in the wire closet - Termination of cables must obey the following: - Twists of actual pairs must be maintained to half-inch of termination. - Cable sheath should be stripped only as far as necessary to terminate. - Cables bundles should not nopt tightly bound or cinched - Cable bundles should not be placed under stress or tension - Cable bend radii should not be less than 8 times the cable diameter

22. Coaxial Cable

23. Coaxial Cable Applications • Most versatile medium • Television distribution • Aerial to TV • Cable TV • Long distance telephone transmission • Can carry 10,000 voice calls simultaneously • Being replaced by fiber optic • Short distance computer systems links • Local area networks

24. Coaxial Cable - Transmission Characteristics • Analog • Amplifiers every few km • Closer if higher frequency • Up to 500MHz • Digital • Repeater every 1km • Closer for higher data rates

25. Coax The outer shield protects the inner conductor from outside electrical signals. The distance between the outer conductor (shield) and inner conductor plus the type of material used for insulating the inner conductor determine the cable properties or impedance. Typical impedances for coaxial cables are 75 ohms for Cable TV, 50 ohms for Ethernet Thinnet and Thicknet. The excellent control of the impedance characteristics of the cable allow higher data rates to be transferred than with twisted pair cable.

26. Coax Advantages • Higher bandwidth • 400 to 600Mhz • up to 10,800 voice conversations • Can be tapped easily (pros and cons) • Much less susceptible to interference than twisted pair

27. Coax Disadvantages • High attenuation rate makes it expensive over long distance • Bulky

28. CABLE SUBSITUTION DATA TYPE CM Communication wires & cables CL2 Class 2 remote control, signaling, & power-limited cables CL3 Class 3 remote control, signaling, & power-limited cables FPL Power limited fire protective signaling cables MP Multi-purpose cables PLTC Power limited tray cable xxR Indicates a RISER cable xxP Indicates a PLENUM cable Plenum is highest grade. Order is : MPP -> CMP -> CL3P -> CL2P; FPLP -> CL3P & 2P Riser is next higher grade. Order is : MPR -> CMR -> CL3R -> CL2R; FPLR -> CL3R & CL2R General Purpose is next. Order is : MP -> CM -> CL3 -> CL2 : FPL or PLTC -> CL3 & CL2 Residential is lowest. The order is : CMX -> CL3X -> CL2X

29. THE CATEGORIES OF CABLE WIRE LEVEL 1 Level 1 cable is for basic comm & power limited circuits. VOICE GRADE ONLY. 2 Level 2 cable is similar to IBM Type 3 cable for 2 to 25 twisted pair cable. 1MHz max. 8db/1000ft attenuation @ 1MHz; 4db/1000ft @ 256KHz. DIGITAL DATA GRADE 3 Level 3 cable is Unshielded Twisted Pair (typical telephone wire). 16MHz max frequency. 7.8db/1000ft attenuation @ 1MHz; 4db/1000ft @ 256KHz. 10Mpbs ENET/ 4Mpbs TR 4 Level 4 cable is Low Loss Premises Telecommunication cable, shielded/unshielded, 20Mhz max 6.5db/1000ft attenuation @ 1MHz; 31db/1000ft @ 20MHz for 24AWG wire 4.5db/1000ft atten @ 1MHz; 24db/1000ft @ 20MHz for 22AWG wire. 16Mbps TR. 5 Level 5 cable is DATA GRADE up to 100Mbit

30. IBM CABLE TYPE 1 Dual pair STP 22AWG solid, non-plenum data cable, used for long runs in walls of buildings 1P Dual pair STP 22AWG, plenum data cable 2 Dual pair STP 22AWG data, 4 pair UTP 24AWG solid, telephone(voice) non-plenum cable 2P Dual pair STP 22AWG data, 4 pair 22AWG telephone plenum cable 3 Multi-pair (usually 4) UTP 22 or 24 AWG solid data & voice cable for runs in walls 5 Two 100/140 micrometer optical fiber in a single sheath 6 Dual pair 26AWG non-plenum patch panel data cable, used for patch panels. Attn=1.5xType1 8 One flat STP of 26AWG stranded wire for under carpet 9 Dual pair STP 26AWG solid non-plenum data cable, Low grade dual pair. Attn=1.5xType1 9P Dual pair STP 26AWG plenum data cable 9R Dual pair STP 26AWG riser data cable Based on general description of cable per IBM definitions

31. Optical Fiber

32. Optical Fiber - Benefits • Greater capacity • Data rates of hundreds of Gbps • Smaller size & weight • Lower attenuation • Electromagnetic isolation • Greater repeater spacing • 10s of km at least

33. Attenuation

34. Optical Fiber - Applications • Long-haul trunks • Metropolitan trunks • Rural exchange trunks • Subscriber loops • LANs

35. Optical Fiber - Transmission Characteristics • Act as wave guide for 1014 to 1015 Hz • Portions of infrared and visible spectrum • Light Emitting Diode (LED) • Cheaper • Wider operating temp range • Last longer • Injection Laser Diode (ILD) • More efficient • Greater data rate • Wavelength Division Multiplexing

36. Fiber Optic Types • Multimode step-index fiber • the reflective walls of the fiber move the light pulses to the receiver • Multimode graded-index fiber • acts to refract the light toward the center of the fiber by variations in the density • Single mode fiber • the light is guided down the center of an extremely narrow core

37. Optical Fiber Optical fiber Optical fiber consists of thin glass fibers that can carry information at frequencies in the visible light spectrum and beyond. The typical optical fiber consists of a very narrow strand of glass called the core. Around the core is a concentric layer of glass called the cladding. A typical core diameter is 62.5 microns (1 micron = 10-6 meters). Typically Cladding has a diameter of 125 microns. Coating the cladding is a protective coating consisting of plastic, it is called the Jacket.

38. Refraction in Fiber An important characteristic of fiber optics is refraction. Refraction is the characteristic of a material to either pass or reflect light. When light passes through a medium, it "bends" as it passes from one medium to the other. An example of this is when we look into a pond of water.

39. Angle of Incidence If the angle of incidence is small, the light rays are reflected and do not pass into the water. If the angle of incident is great, light passes through the media but is bent or refracted. Optical fibers work on the principle that the core refracts the light and the cladding reflects the light. The core refracts the light and guides the light along its path. The cladding reflects any light back into the core and stops light from escaping through it - it bounds the medium!

40. Optical Fiber Transmission Modes

41. Step Index Step index has a large core, so the light rays tend to bounce around inside the core, reflecting off the cladding. This causes some rays to take a longer or shorter path through the core. Some take the direct path with hardly any reflections while others bounce back and forth taking a longer path. The result is that the light rays arrive at the receiver at different times. The signal becomes longer than the original signal. LED light sources are used. Typical Core: 62.5 microns. Step Index Mode

42. Graded Index Graded index has a gradual change in the core's refractive index. This causes the light rays to be gradually bent back into the core path. This is represented by a curved reflective path in the attached drawing. The result is a better receive signal than with step index. LED light sources are used. Typical Core: 62.5 microns. Graded Index Mode

43. Single Mode Single mode has separate distinct refractive indexes for the cladding and core. The light ray passes through the core with relatively few reflections off the cladding. Single mode is used for a single source of light (one color) operation. It requires a laser and the core is very small: 9 microns. Single Mode

44. Comparison of Optical Fibers

45. Loose Tube Fiber Non-armored Armored

46. FIBER OPTIC LINK SUMMARY

47. A Fiber Connector

48. Fiber Connectors

49. Splicing Avg. Splice Loss (dB)Fusion Splicing 0.10 dBRotary Mechanical* 0.20 dBMechanical Splice 0.20 dB Splicing Technologies Splicing technologies may be divided into two basic categories: fusion and mechanical. Mechanical methods may include products that use mechanical means to align two cleaved fibers or products that require polishing of the fiber ends. Return Loss Return loss is the measure of the level of signal reflected by the splice back to the source. Return loss of 40 dB or better is needed to assure proper performance for analog video transmission over fiber.

50. DWDM DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber. In effect, one fiber is transformed into multiple virtual fibers. So, if you were to multiplex eight OC -48 signals into one fiber, you would increase the carrying capacity of that fiber from 2.5 Gb/s to 20 Gb/s. Currently, because of DWDM, single fibers have been able to transmit data at speeds up to 400Gb/s. And, as vendors add more channels to each fiber, terabit capacity is on its way. A key advantage to DWDM is that it's protocol and bit-rate independent. DWDM-based networks can transmit data in IP, SONET/SDH, Ethernet, and handle bit-rates between 100 Mb/s and 2.5 Gb/s. Therefore, DWDM-based networks can carry different types of traffic at different speeds over an optical channel.