Maximum distance of LAN Cables.

What is the maximum distance of a LAN Cable or Fiber ?

Type	Cable used	IEEE standard	Distance
10BASE2 (obsolete)	Thick coaxial		185 m
10BASE5 (obsolete)	Thin coaxial		500 m
10BASE-T (obsolete)	UTP Cat 3		100 m
100BASE-TX	UTP Cat 5	IEEE 802.3u	100 m
100BASE-FX	Fiber Multimode		400 m
1000BASE-LX	LongWavelength Laser		10 km (SM), 3 km (MM)
1000BASE-SX	ShortWwavelength Laser		220 m with 62.5u MM 550 m with 50u MM
1000BASE-ZX	Extended wavelength		100 km, SM

Which wavelengths are used in optic fibers?

650nm,850nm in plastic optic fiber

850nm,1300nm in multimode graded index optic fiber

1300nm, 1490 to 1625nm in singlemode optic fiber

 

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Whether these are ultraviilet or infra-red?

 

We are ablel to see between 400nm to 700nm. Above 700nm is infra red. So fibers use infra red.

850,1300,1550 are the common wavelengths used in fibers.

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Why we have to use certain specific wavelengths like 850,1300,1550?

Attenuation is due to scattering and absorption.

When wavelength increases, attenuation decreases, That is why, we use above 850.

The frequencies lying between 850 and 1300 as well as between 1300 and 1500 are called as WATER BANDS.

The fiber is having water vapour. This vapour absorbs the em waves in these range very easily.

plastic fiber have low absorption, so even at 650nm we are able to use it.

 

 

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1300nm is long wave, 850nm is shortwave

 

LAN Interview Questions - Part 2

LAN interview questions and answers

LAN NETWORK interview questions (part-2)

More Knowledge is NOT good for health. However, it is given here. You take it or leave it !

 

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1. What is the voltage levels used in 10BaseT?

In case of 10Base T, +2.5V and -2.5V

In case of 100Base T, three voltage levels are used: +1V, 0v, -1V

1000BaseT uses, five voltage levels, all the four pairs are used, CAT5E cable is used.

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2. What is AUTO-MDI-X?

MDI-X is cross over cable. When you are connecting a switch to another switch, you need cross over cable. if the port is having auto mdi-x facility, then you can use straight cable. The port itself will sense and change over to cross over mode. Normally, if the ports are having this facilty, then it will marked as 1x,2x,3x,etc instead of 1,2,3,etc.

 

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3. What modulation technique is used in case of 1000BaseT?

PAM

 

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4. What is the maximum length of cat5 cable between pc and switch?

100 meters.

 

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5. For wiring RJ45 which standard should be used.T568A or T568B?

You can use either of them for straight cable.

For crossover cable, it is better to use T568A for one end and T568B for the other end.

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6. In the ethernet port of my computer, which pins are trans and which pins are receive?

pin 1,2 is trans. pin 3,6 is receive.

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7. The hub uses star topology or bus topology?

Eventhough, the physical connection looks like star topology, it is logically bus topology.But From exam point of view, always write STAR TOPOLOGY.