DCN286 INTRODUCTION TO DATA COMMUNICATION TECHNOLOGY

Network Cable Testers and Tests

Digital Signal Transmission

1. By varying an electrical signal when it passes over a wire that is typically made of copper.

2. By varying the power of light as sent over a glass optical fiber.

3. By varying the radio waves sent through space, which is commonly referred to as wireless communications.

Common terminologies in waves

• Amplitude: height of wave (volt, meter, amp, etc, etc) which usually means strength of waves.

• Frequency: number of waves per second (hertz=1/second). High frequency means more waves coming in one second.

• Period: time between each waves. Higher period also means lower frequency (less waves coming in each second)

Sine wave

- Periodic

- Continuously varying

- T = 1/F (T: period; F: frequency)

Square wave

- Periodic

- NOT continuously varying

- T = 1/F (T: period; F: frequency)

Other waves (Optional)

• Triangle

• Sawtooth

Analog and digital wave

• Analog wave: usually refers to sine wave as it can easily presents many natural events.

• Digital wave: usually associated with square wave because it presents binary digits.

Combined waves

• Frequency of wave 1 is 300 hz

• Frequency of wave 2 is 500 hz

• When they are added together, blue wave presents the complex combined wave.

Signals and Noise

• Signal: the desired binary digits presented by the energy (electric, light and radio) transmission.

• Noise: any environmental interference while receiver detects the data signal.

• Other factors might degrade signals: grade of the cable, connector and installation (connection), distance of cable connection and network design.

Impedance and attenuation

• Impedance contains the material resistance and other resistant forces in a circuit.

• Attenuation- the amount of signals that a cable will absorb is a measure of its attenuation. Lower attenuation indicates higher quality conductors and cables.

• Voltage (electrical power) and light power would decrease while travelling alone copper wires and optic fiber cables.

Coaxial cable

• Shield must be grounded.

• Plastic jacket can offer protection against moisture and insulation.

STP (Shielded Twisted Pair) cable

• Shielding provides better electrical signals by reducing noise and attenuation.

• Shielding makes the cable more expensive, heavier and hard to bend.

STP - 3 insulations

• Total 3 insulations:1.Each thin wire is covered

in color-coded plastic insulation

2.Each pair of wires is twisted with a insulator called a pair shield around them

3.All the wires in the cable (usually 4 pairs) are covered by a shield called the overall shield.

Single bit

• In a 100Mbps cable transmission, how long will a bit be sent/received?

1/100,000,000 of 1 second

(100,000,000b = 100Mb)

UTP (Unshielded Twisted Pair)

• Twist offers the resistance to interference!!!

• Flexible and easy install

• Offer the same data speeds

• Inexpensive

• RJ45 connector (RJ11 is for phone cable).

Ethernet Extender (optional)Three primary purposes:• Extend network coverage; • Maintain the bandwidth; • Control budget or TOC (Total Owner Cost)

TIA/EIA568-A and B pin outs

Pin # Function 568A wire color 568 B wire color

1 TD+ White/Green White/Orange

2 TD- Green Orange

3 RD+ White/Orange White/Green

4 Unused Blue Blue

5 Unused White/Blue White/Blue

6 RD- Orange Green

7 Unused White/Brown White/Brown

8 Unused Brown Brown

Cable Specifications

Coaxial Cable

Shielded Twisted-Pair Cable

Unshielded Twisted Pair (UTP)

Unshielded Twisted Pair (UTP)

Unshielded Twisted Pair (UTP)

Straight Through Cable

Unshielded Twisted Pair (UTP)

Cross-Over Cable

Unshielded Twisted Pair (UTP)

Roll-over Cable

How to maintain quality

• Well network design (will be taught later)

• Certified technician who usually has better installation knowledge

• Certified cables (better quality connectors and cables)

• Well insulation (new cable usually does not have broken insulation )

• Environment check and tests.

Crosstalk

When current flows over a nearby wire, it generate EMI and cause crosstalk.

• Near-end crosstalk (NEXT)• Far end crosstalk (FEXT)• Power sum near-end crosstalk (PSNEXT)

How to read NEXT?NEXT is expressed as a negative value of

decibels. -30dB means less NEXT.

NEXT (Near-end crosstalk)

• It occurs near the source of the test signal

• NEXT current direction is opposite to the transmitted test signal direction

• Test signal and NEXT test are on same side of the connection.

FEXT (Far End Crosstalk)

• Used to test crosstalk in the same circumstances of NEXT

• The only difference to NEXT is to detect a signal crossing (disruption) that is located at a distance from the point of measurement.

• FEXT may cause less noise than NEXT

PSNEXT (Power sum Near-end Crosstalk)• PSNEXT is to add all

pairs’ NEXT together.

• Becomes a part of TIA/EIA 568B tests.

Standard Tests for Cable certification

• Wire map: Identify physical error of any miss-wiring• Insertion loss: Lose of signal strength, expressed in dB.• NEXT: A higher value is desirable, meaning better cable performance• PSNEXT: Combined NEXT• Equal-level Far-end Crosstalk (ELFEXT): FEXT is usually less detrimental

to a signal than NEXT• Power sum equal-level far-end crosstalk (PSELFEXT): sum of all FEXT• Return loss: measured in dB and indication of bad crimp or bad connection

at the RJ45 plug.• Propagation delay: tests for the time it takes for the signal to be sent from

one end and received by the other end • Cable length: Verify not exceed 100m. Also find shortcut or where the

broken point is• Delay skew: Tests for difference between the fastest and slowest set of

wire pairs. Lower is better. Could be between 25-50 nanoseconds over 100m

Professional cable certification tester

Fluke DTX CableAnalyzer

LT8000 Series Cable Certification Tester

Copper cable certification is achieved through a thorough series of tests in accordance with Telecommunications Industry Association (TIA) or International Organization for Standardization (ISO) standards.

Testers

• Regular DC/AC voltmeters, Ammeters, and Ohmmeters (multimeter)

• Signal testers: function generators, pulse generators, RF signal generators, sine wave sources, etc, etc.

• Oscilloscope and mixed signal probes• Wave form measurements: square wave test, Time

Domain Reflectometer, Diode I-V characteristic, • Electronic Counters: frequency dividers, Period

measurement, Reciprocal counter, Universal counter,

• Power supplies and remote sensing• Spectrum and network analyzers• Logic Analyzers: Logic analyzer, timing analyzer, Mi

Some basic cable testers

PatchTest Ethernet Cable Tester

Other Ethernet cable tester• Connect cable

between receiver and transmitter.

• Push button sending test signals

Time Domain Reflectometer

Tone tester (optional)

• Such tester can be used to identify termination point of wires or to trace their paths

Test telephone (optional)

• Easy to be used to verify phone line connection

Online Internet Bandwidth Tests

Many websites can be used to test internet upload and download speed:

www.speedtest.net

www.bandwidthplace.com/

www.speakeasy.net/speedtest

http://reviews.cnet.com/internet-speed-test/

www.toast.net

http://promos.mcafee.com/speedometer/test_0600.asp (McAfee internet

Connection Speedometer)

LAN speed test

Many free software programs are available:

Iperf bandwidth test (http://lss.rutgers.edu/index.php?page=tool_iperf)

QCheck (http://www.ixchariot.com/products/datasheets/qcheck.html)

Bandwidth Monitor(http://www.supershareware.com/info/bandwidth-monitor.html)

Real Time NetFlow Analyer(http://www.solarwinds.com/products/freetools/

netflow_analyzer.aspx)

Network monitor (optional)

Network Analyzer (optional)

1. Hardware equipmentThe two main categories of Network

Analyzers are• Scalar Network Analyzer (SNA) -

Measures amplitude properties only

• Vector Network Analyzer (VNA) - Measures both amplitude and phase properties,

2. Software used for network analyzerWireshark, Ethereal, CommView,

Network Sniffer, Network Packet Analyzer, Distinct Network Monitor, etc, etc

Use light energy• Electrical signal use on (high voltage) and off

(low voltage) to transmit 1 and 0 in copper cable.• Light signal can also use on (brighter light) and

off (dim light) to transmit 1 and 0 in fiber-optic cables.

EM spectrumAudi Radio Microwaves Infrared Ultra-

violet X Rays Gamma Rays

In the line, wave length is reducing and frequency is increasing.

Optic media

• Fiber-optic cable has the strongest ability to resist EMI (electromagnetic interference), RFI (Radio Frequency Interference)

• Fiber’s bandwidth is much higher than any other media.

• Fiber is highly secure and it is easy to detect intrusion.

• Fiber uses light signal transmission and its attenuation is much less than electrical signals. Its length could be very long

Optic fiber cable testers• SimpliFiber

Optical Loss Test kits

• FiberViewer

• Fiber Optic Cleaning Kits

Optical fiber Test

• The tester may have curve display

• Or, it has numeric output

• Certifies compliance of multimode fiber networks to industry standards. Can test two fibers at two wavelengths simultaneously with one-button Autotest

Wireless tech introduction

• Infrared• Bluetooth• Microwave• Radio• Wi-Fi

In general, wireless network is secondary because of two concerns: speed and security. But, it does offer mobility and convenience.

Main wireless components• Access point: linking wireless network to

the wired world.

• Wireless NIC on each hosts in the network

• Wireless hub, switch and router: functioning as same as regular wire connected equipments

Introduction of Wireless Testers (optional)

• Real Time Spectrum Analyzer

• RF environment scanner

Question

Any question?

If you do not have question, please search internet and collect more information of those cables testers and test standards.

1. Please be comfortable to list the pin wire colors.

2. Please be familiar with those testing concepts.