Chapter 4 - Backbone Distribution Systems

Question 1

When designing an in-building backbone distribution system using slots, up to _____ of useable floor space can be served by one slot sized at 0.04 m2 (60 in2).

a. 1858 m2 (20,000 ft2)
b. 3716 m2 (40,000 ft2)

Answer 1

b. 3716 m2 (40,000 ft2)

p 4-46

The size of the pathway using slots should be one slot sized at 0.04 m2 (60 in2) for up to 3716 m2 (40,000 ft2) of usable floor space served by that backbone
distribution system.

The slot area should be increased by 0.008 m2 (12 in2) with each 3716 m2 (40,000 ft2) increase in usable floor space served by that backbone.

Question 2

A backbone star topology shall have no more than _____ level(s) of cross connection.

a. One
b. Two
c. Three
d. Four

Answer 2

b. Two

p 4-27

A backbone star topology shall have no more than two levels of cross-connections.

Connections between any two HCs (FDs) shall not pass through more than three cross connections.

Question 3

A slot used for backbone distribution is typically placed flush against the wall and should have a minimum depth of _____ perpendicular to the wall.

a. 76 mm (3 in)
b. 152 mm (6 in)
c. 127 mm (5 in)
d. 100 mm (4 in)

Answer 3

d. 152 mm (6 in)

p 4-46

Slots are typically located flush against the wall within a space and should be designed at a depth (the dimension perpendicular to the wall) of ≈152 to 610 mm (6 to 24 in), giving preference to narrower depths wherever possible

Question 4

In a 1000BASE-X point-to-point (PTP) passive optical network (PON), the _____ is responsible for media conversion from the optical fiber to the balanced twisted-pair (or other media) in the home.

a. Optical network unit
b. Optical network terminal
c. Optical line terminal
d. Optical splitter

Answer 4

b. Optical network terminal

p 4-18

Figure 4.13 shows the topology of a PTP network over optical fiber. Multiple devices in the home can be connected to a single Ethernet port from the home to the carrier. The ONT is responsible for media conversion from the optical fiber to the balanced twisted-pair network or other media in the home.

Note, ONU is used for PTMP

Question 5

The aggregation device, called the OLT, supports a minimum of ___ subscribers per port by means of a passive optical splitter.

a. 8
b. 10
c. 16
d. 32

Answer 5

d. 16

p 4-18

The EFM objective to support EPONs is based on a number of economic advantages. The aggregation device, called the OLT, supports a minimum of 16 subscribers per port by means of a passive optical splitter.

Question 6

Balanced twisted-pair and optical fiber backbone cabling:

a. Must always be in separate sheaths
b. May be combined under a single sheath

Answer 6

b. May be combined under a single sheath

p 4-37

A building cabling system shall have only one MC (CD). Connection to the ER can then be provided by balanced twisted-pair or optical fiber, which is either in separate sheaths or combined under a single sheath (see Figure 4.25).

Question 7

ITU-T EFM installed singlemode optical fiber ___ which is dispersion unshifted fiber.

a. G.652
b. G.653
c. G.655
d. G.656
e. G.657

Answer 7

a. G.652

p 4-20 Table 4.2

G.652.B 1300 to 1324 nm Supports 1 Gigabit Ethernet, 10 Gigabit Ethernet and SONET. Supports some higher bit rate applications, (e.g., STM-64, STM-256) depending on the system architecture.

Question 8

ITU-T EFM installed singlemode optical fiber ___ which is dispersion unshifted fiber.

a. G.652
b. G.653
c. G.655
d. G.656
e. G.657

Answer 8

a. G.652

p 4-20 Table 4.2

G.652.B 1300 to 1324 nm Supports 1 Gigabit Ethernet, 10 Gigabit Ethernet and SONET. Supports some higher bit rate applications, (e.g., STM-64, STM-256) depending on the system architecture.

Question 9

ITU-T EFM installed singlemode optical fiber ___ which is dispersion Shifted fiber.

a. G.652
b. G.653
c. G.655
d. G.656
e. G.657

Answer 9

b. G.653

p 4-20 Table 4.2

G.653.A 1525 to 1575 nm Supports STM-64 and SDH systems with an unequal channel spacing in the 1550 nm wavelength region.

Question 10

ITU-T EFM installed singlemode optical fiber ___ which is Non-zero dispersion shifted fiber.

a. G.652
b. G.653
c. G.655
d. G.656
e. G.657

Answer 10

c. G.655

p 4-20 Table 4.2

G.655.C 1530 to 1565 nm C and L-band compatible

Question 11

ITU-T EFM installed singlemode optical fiber ___ which is wideband non-zero dispersion shifted fiber.

a. G.652
b. G.653
c. G.655
d. G.656
e. G.657

Answer 11

d. G.656

p 4-21 Table 4.2

Question 12

ITU-T EFM installed singlemode optical fiber ___ which is bending loss insensitive fiber.

a. G.652
b. G.653
c. G.655
d. G.656
e. G.657

Answer 12

e. G.657

p 4-21 Table 4.2

Compatible with ITU-T G.657.A (and ITU-T G.652.D) fibers and systems within access networks. Suitable for transmission at 1310, 1550, and 1625 nm for restricted distances.

Question 13

In Ethernet over digital subscriber line (EoDSL) networks, service is provided to subscribers in a _____ topology using balanced twisted-pair cable.

a. PTP
b. PTMP

Answer 13

a. PTP

p 4-22

Ethernet over point-to-point (PTP) balanced twisted-pair cable is probably the best fit for established neighborhoods, business parks, and multi-dwelling units because it can re-sue the existing first mile of voice grade, balanced twisted-pair cable (see Figure 4.14).

Termed EoDSL, rate names include 10PASS-T (10 Mb/s) for short reach up to ≈750 m (2461 ft) and 2PASS-TL (2 Mb/s) for long reach up to ≈2700 m (8858 ft).

Question 14

Within a fully connected mesh topology there are a total of 10 nodes. How many links are required to complete the network?

a. 25
b. 30
c. 45
d. 50

Answer 14

c. 45

p 4-16

N = number of links
X = number of nodes
N = (X * (X-1)) / 2
or (10 * 9) / 2, 90/2 = 45

Question 15

Sleeves should be located a minimum of ___ from the wall or between adjacent sleeves to provide room for bushings, but not so far from the wall that it would be a tripping hazard or create too great a cable span from the sleeve to the backboard/tray.

a. 100 mm (4 in)
b. 75 mm (3 in)
c. 50 mm (2 in)
d. 25 mm (1 in)

Answer 15

d. 25 mm (1 in)

p 4-43

Construct all:
• Slots and sleeves to conform to appropriate codes and standards.
• Slots with a minimum ≈25.4 mm (1 in) high curb.
• Sleeves to extend a minimum of ≈25.4 mm (1 in) above the floor level and a maximum of ≈77 mm (3 in) above the floor level.

Question 16

Cable trays can be used as vertical cable pathways for general backbone cable distribution between vertically aligned telecommunications rooms.

a. True
b. False

Answer 16

a. True

p 4-46

A cable tray can be used as a vertical cable pathway within shafts or as part of the pathway between vertically aligned TRs. A cable tray can be open or covered and provides a means for attaching vertical cable runs to the cable tray members.

Question 17

The recommended balanced twisted-pair cable for building backbones consists of round, solid copper conductors up to ____ AWG in diameter.

a. 22
b. 23
c. 24
d. 26

Answer 17

a. 22

p 4-38

The recommended balanced twisted-pair cable for building backbone consists of 24 AWG or up to 22 AWG round, solid copper conductors with a nominal characteristic impedance of 100 ohm.

Question 18

The recommended multimode optical fiber for a building backbones is OM3.

a. True
b. False

Answer 18

b. False

p 4-38

OM4 or higher is recommended.

Question 19

In a backbone star topology, connections between any two floor distributors shall not pass through more than _____ cross-connector(s).

a. 1
b. 2
c. 3
d. 4

Answer 19

c. 3

p 4-27

A backbone distribution system shall have no more than two levels of cross-connections. Connections between any two HCs (FDs) shall not pass through more than three cross-connections (see Figure 4.17).

Question 20

In a hierarchical star building backbone for a high-rise building, the same telecommunications room could house connecting hardware to serve the function of the:

a. MC (CD) and IC (BD)
b. HC (FD) and MC (CD)
c. IC (BD) and HC (FD)

Answer 20

c. IC (BD) and HC (FD)

p 4-34

The same TR could house connecting hardware to serve the function of the IC (BD) and HC (FD).

Question 21

The maximum balanced twisted-pair backbone length for voice systems should not exceed:

a. 1200 m (3936 ft)
b. 1000 m (3280 ft)
c. 800 m (2625 ft)
d. 500 m (1649 ft)

Answer 21

c. 800 m (2625 ft)

p 4-39

In addition to the ≈800 m (2625 ft) backbone cable length for voice systems, total length between network equipment connections should not be greater than ≈100 m (328 ft).

Question 22

In a typical hierarchical star campus backbone, the link from the MC (CD) to the IC (BD) is an:

a. Interbuilding or intrabuilding link
b. Interbuilding link
c. Intrabuilding link

Answer 22

a. Interbuilding or intrabuilding link

p 4-6

In typical applications, the link from the:
• MC (CD) to IC (BD) may be an interbuilding or intrabuilding link.
• IC (BD) to HC (FD) will typically be an intrabuilding link.

Question 23

Category 5e multi-pair backbone balanced twisted-pair cable is commonly available in 4 pair and ____ pair configurations.

a. 250
b. 100
c. 50
d. 25

Answer 23

d. 25

p 4-39

Category 5e is commonly available in 4 pair and 25 pair configurations

Question 24

Category 3 is available in 4 pair through 2500 pair configurations.

a. True
b. False

Answer 24

b. False

p 4-39

Category 3 is available in 4 pair through 2700 pair configurations

Question 25

Singlemode fiber is suitable for use with both analog and digital transmission.

a. True
b. False

Answer 25

a. True

p 4-38

Question 26

Cables containing both ____ are often recommended for backbone use in order to satisfy present and future needs.

a. Singlemode optical fibers and balanced twisted-pairs
b. Balanced twisted-pairs and multimode optical fibers
c. Multimode and singlemode optical fibers

Answer 26

c. Multimode and singlemode optical fibers

p 4-40

Often, a backbone comprised of both multimode and singlemode optical fiber is recommended to satisfy present and future needs in the backbone.

Question 27

Backbone cabling interfaces to the horizontal cabling in a:

a. Telecommunications room or telecommunications enclosure
b. Telecommunications room

Answer 27

a. Telecommunications room or telecommunications enclosure

p 4-31

A TR or TE is a point where the backbone cabling interfaces to the horizontal cabling.

Question 28

Campus and wide area backbone cabling and infrastructure is the network segment _____ affected by physical considerations.

a. Most
b. Least

Answer 28

a. Most

p 4-3

Campus and wide area backbone cabling and infrastructure is also the network segment most affected by physical considerations (e.g., infrastructure availability, private easements, public R/W, physical barriers, security, and environmental restrictions).

Question 29

The most common application for optical fiber backbone cabling is multiplexed transmission.

a. True
b. False

Answer 29

a. True

p 4-50

The most common application for optical fiber backbone cabling is multiplexed transmission. In multiplexed transmission, multiplexing equipment in TRs and ERs combines signals from many end points for transmission over two strands of optical fiber.

Question 30

In Ethernet over digital subscriber line (EoDSL) networks, 2 Mb/s service can be provided to subscribers over a maximum span of _____ using balanced twisted-pair cable.

a. 2700 m (8858 ft)
b. 1500 m (4920 ft)
c. 1700 m (5576 ft)
d. 2500 (8200 ft)

Answer 30

a. 2700 m (8858 ft)

p 4-22

Termed EoDSL, rate names include 10PASS-T (10 Mb/s) for short reach up to ≈750 m (2461 ft) and 2PASS-TL (2 Mb/s) for long reach up to ≈2700 m (8858 ft). “Nike at Kohl’s”.

Question 31

Ethernet in the first mile (EFM) _____ physical layer signaling operates over one or more pairs of voice grade balanced twisted-pair cable.

a. 2BASE-TL
b. 2PASS-T

Answer 31

a. 2BASE-TL

p 4-54 Table 4.4

Question 32

When there are direct connections between telecommunications rooms (TRs) for a bus or ring configuration, these direct connections are _____ the connections for the star or hierarchical star topology.

a. In place of
b. In addition to

Answer 32

b. In addition to

p 4-31

These direct connections would be in addition to the connections for the star or hierarchical star topology.

Question 33

The loop distance range in an “ethernet in the first mile” (EFM) design is:

a. 2 km (1.2 mi)
b. 4.8 km (3 mi)
c. 6.1 km (3.8 mi)
d. 9.7 km (6 mi)

Answer 33

c. 6.1 km (3.8 mi)

p 4-53

In reference to Figure 4.28, the loop distance range is up to ≈6.1 km (20,013 ft).

Question 34

One advantage of using pre-connectorized jumpers and cables is:

a. They are less costly than field connectorized connectors
b. The cables are more rugged and can handle higher pull tensions
c. They come with factory certified quality of terminations
d. They require additional engineering time thereby providing a higher degree of reliability

Answer 34

c. They come with factory certified quality of terminations

Question 35

You have been asked to design a backbone cable connecting two large campus buildings. Your pathways will include using conduits, maintenance holes, and one section of 100 m (328 ft) of direct buried optical fiber cable. Your choice of fiber optic cable type recommendation is a:

a. Distribution cable
b. Loose tube cable
c. Loose tube cable containing a water blocking compound
d. Distribution cable with an armored coating

Answer 35

c. Loose tube cable containing a water blocking compound

Question 36

Multimode optical fiber is generally used for campus or building applications due to the ability to use cost effective:

a. Connectors
b. Cable
c. Installation methods
d. Transceivers

Answer 36

d. Transceivers

Question 37

The decision regarding the number of optical fibers to install (fiber strand count) in a backbone depends largely on all of the following EXCEPT:

a. Level of multiplexing
b. Intended end-user applications
c. Physical topology of the cabling system
d. Distance between telecommunications room (TR)

Answer 37

d. Distance between telecommunications room (TR)

Question 38

When installing a heavy backbone cabling vertically, recommended methods of securing the cable include all of the following EXCEPT:

a. Tie wraps
b. Brackets
c. Steel or plastic straps

Answer 38

a. Tie wraps

Question 39

You are reviewing a building backbone design with a vertically aligned telecommunications room (TR). In the spec you note in a footnote with details that the slots at one end of the telecommunications room (TR) must be flush with the floor and the sleeves provide at the end of the telecommunications room (TR) must also be flush. In your meeting with the electrical engineering firm that has provided the spec, you make the comment that according to best practices, the MINIMUM that slots and sleeves must extend above the finished floor are:

a. 25 mm (1 in) for slots and 51 mm (2 in)
b. 25 mm (1 in) for slots and 25 mm (1 in)
c. 51 mm (2 in) for slots and 25 mm (1 in)
d. 51 mm (2 in) for slots and 51 mm (2 in)

Answer 39

b. 25 mm (1 in) for slots and 25 mm (1 in)

p 5-81

Terminate conduits that protrude through the structural floor ≈25 mm (1 in) to ≈77 mm (3 in) above the surface.

Question 40

When reviewing a backbone distribution system within a building provided to you for standards compliance, you see that there are several cables with bridge taps built in. Which one of the following options is correct?

a. Ensure all cables meet maximum lengths to ensure standards compliance
b. Ensure all cables exceed minimum cable lengths to avoid NEXT(near-end crosstalk)
c. Provide recommendations to remove all bridge taps
d. Provide recommendations to remove one bridge tap per cable

Answer 40

c. Provide recommendations to remove all bridge taps

Question 41

When designing a backbone distribution system, you are asked to include a combination of media types. Your choice of media types include:

a. Fiber and wireless only
b. Fiber and coaxial cable only
c. Wireless and coaxial cable only
d. Any combination of copper, fiber, and wireless

Answer 41

d. Any combination of copper, fiber, and wireless

Question 42

When designing a backbone distribution system, you will need to include a telecommunications enclosure (TE). A TE can be defined as a:

a. Splice point for copper cabling only
b. Point where the backbone cabling interfaces to the horizontal cabling and may be utilized in place of a traditional Telecommunications Room (TR)
c. Location for housing building cross-connect cabling only
d. Location to house the splice transitioning from outdoor to indoor cabling only

Answer 42

b. Point where the backbone cabling interfaces to the horizontal cabling and may be utilized in place of a traditional Telecommunications Room (TR)

p 4-31

A TR or TE is a point where the backbone cabling interfaces to the horizontal cabling.

Question 43

Which of the following statements best describes what a backbone distribution system typically provides?

a. Cabling from the HC to the WA
b. Pathway from the HC to the WA
c. Conduit in a building riser
d. Building connections between floors in a multistory building

Answer 43

d. Building connections between floors in a multistory building