Chapter 11 - Field Testing of Structured Cabling

Question 1

When testing optical fiber cabling, visual fault locators (VFLs) can be used to verify polarity and to help identify some causes of signal loss. The range of wavelength for visual lasers used for VFLs is generally 850 nm, 1300 nm, and 1550 nm.

a. True
b. False

Answer 1

b. False

p 11-19

The range of wavelengths for visual lasers for VFLs is generally 635 nm, 650 nm, and 670 nm.

The VFL can be used to verify polarity and to help identify some causes of signal loss (e.g., breaks, bends, faulty connectors, splices).

Question 2

When testing optical fiber cabling, polarity can be verified with an optical loss test set (OLTS) while performing attenuation tests or by using a a visible light source.

a. True
b. False

Answer 2

a. True

p 11-19

Polarity can be verified with an OLTS while performing attenuation tests or by using a visible light source (e.g., VFL).

For array connector polarity, test instruments are available to verify the polarity method utilized while also providing attenuation measurements for each optical fiber.

Question 3

In a balanced twisted-pair cable, a wiremap test will NOT indicate a grounded conductor.

a. True
b. False

Answer 3

b. False

p 11-1

In a balanced twisted-pair cable, the test should indicate:
• Continuity to the remote end.
• Shorts between any two or more conductors.
• Transposed pairs.
• Reversed pairs.
• Split pairs.
• Shield continuity (e.g., only for shielded cabling).
• Grounded conductor.

Question 4

Level ___ field test instruments are required for measurements up to 100 MHz for category 5e and class D cabling.

a. IIe
b. III
c. IIIe
d. IV

Answer 4

a. IIe

p 11-15

Question 5

Level ___ field test instruments are required for measurements up to to 250 MHz for category 6 and class E cabling

a. IIe
b. III
c. IIIe
d. IV

Answer 5

b. III

p 11-15

Question 6

Level ___ field test instruments are required for measurements up to category 6A (500 Mhz) and class EA cabling.

a. IIe
b. III
c. IIIe
d. IV

Answer 6

c. IIIe

p 11-15

Question 7

Level ___ has been defined for the measurements of class F/FA balanced twisted-pair cabling up to 1000 MHz.

a. IIe
b. III
c. IIIe
d. IV

Answer 7

d. IV

p 11-15

At present, there are no defined tester accuracy levels for field testers to cover the requirements for class F products up to their 1000 MHz performance capability.

Question 8

When testing optical fiber cabling, the worst-case attenuation coefficient for 50/125 mm and 62.5/125 mm multimode optical fiber at a wavelength of 1300 nm is:

a. 3.5 dB/km
b. 3.0 dB/km
c. 1.5 dB/km
d. 1.0 dB/km
e. 0.4 dB/km

Answer 8

c. 1.5 dB/km

p 11-23 See Table 11.1

Question 9

When testing optical fiber cabling, the worst-case attenuation coefficient for 50/125 laser-optimized OM3 and OM4 optical fiber at a wavelength of 850 nm is:

a. 3.5 dB/km
b. 3.0 dB/km
c. 1.5 dB/km
d. 1.0 dB/km
e. 0.4 dB/km

Answer 9

b. 3.0 dB/km

p 11-23 See Table 11.1

Note, this differs from p 6-15 Table 6.5 - Optical fiber cable transmission performance parameters - where it states 3.5 dB/km loss for both OM3 & OM4. But 1.5 dB/km is correct for all multimode operating at 1300 nm.

Question 10

When testing optical fiber cabling, the worst-case attenuation coefficient for 50/125 for SWDM optical fiber at a wavelength of 1300 nm is:

a. 3.5 dB/km
b. 3.0 dB/km
c. 1.5 dB/km
d. 1.0 dB/km
e. 0.4 dB/km

Answer 10

c. 1.5 dB/km

p 11-23 See Table 11.1

Question 11

Connector attenuation (dB) = Number of connector pairs (N) × connector loss (dB) or = N × ___ dB

a. 0.30
b. 0.50
c. 0.75
d. 1.0

Answer 11

c. 0.75

p 11-23

Question 12

Splice attenuation (dB) = Number of splices (S) × splice loss (dB) or = S × ___ dB

a. 0.30
b. 0.50
c. 0.75
d. 1.0

Answer 12

a. 0.30

p 11-23

Note, this is the typical maximum value from p 1-113 Table 1.36 - Splice loss values in decibels:

Table 1.36 - Multimode & Singlemode
Splice Type_____Average____Maximum
Fusion__________0.05________0.3
Mechanical_______0.10________0.3

Question 13

When testing balanced twisted pair cabling, testing to a MUTOA or CP is subject to _____ test requirements

a. End-to-end
b. Channel
c. Permanent link
d. Horizontal link

Answer 13

c. Permanent link

p 11-17

Testing to a MUTOA or CP (known as the CP link) is subject to permanent link test requirements.

For example, the CP link comprises horizontal cabling from the patch panel in the ER to the CP. The pass/fail limits are based on up to ≈90 m (295 ft) horizontal cable plus two connectors. The permanent link, including the CP, should be tested after installation of the open office cabling.

Question 14

Characteristic impedance is a required acceptance test on balanced twisted-pair cabling

a. True
b. False

Answer 14

b. False

p 11-3

Characteristic impedance is not required as an acceptance test for balanced twisted-pair cabling.

In some cases, a test may refer to an impedance measurement as the characteristic impedance of the cable. The measurement is more often the input impedance and usually is only an approximation.

Question 15

When field testing singlemode optical fiber cabling, to promote efficient and accurate testing, the light source or OTDR must operate within the range of 1310 nm:

a. ± 40 nm
b. ± 30 nm
c. ± 20 nm
d. ± 10 nm

Answer 15

d. ± 10 nm

p 11-24

The light source or OTDR must operate within the range of 1310 ± 10 nm or 1550 ± 20 nm for singlemode testing.

Question 16

When field testing multimode optical fiber cabling, to promote efficient and accurate testing, the light source or OTDR must operate within the range of 1300 nm:

a. ± 40 nm
b. ± 30 nm
c. ± 20 nm
d. ± 10 nm

Answer 16

c. ± 20 nm

p 11-24

The light source or OTDR must operate within the range of 850 ± 30 nm or 1300 ± 20 nm for multimode testing.

Question 17

When testing optical fiber cabling, the worst-case attenuation coefficient for 50/125 mm and 62.5/125 mm multimode optical fiber at a wavelength of 850 nm is:

a. 3.5 dB/km
b. 3.0 dB/km
c. 1.5 dB/km
d. 1.0 dB/km
e. 0.4 dB/km

Answer 17

a. 3.5 dB/km

p 11-23 See Table 11.1

Note, it’s the only 3.5 dB/km value in the table.

Question 18

When using the TDR method to calculate the length of a balanced twisted pair cable, the time it takes a pulse to travel down the cable and back is called the:

a. Channel delay
b. Path delay
c. Propagation delay
d. Round trip delay

Answer 18

d. Round trip delay

p 11–3

A TDR method is used to calculate the length of a cable by measuring the time it takes a pulse to travel down the cable and back (round-trip delay).

Eq:
Cable length = (NVP × (round-trip delay) × c × 110%) / 2

Question 19

When testing multimode optical fiber cabling, an OTDR typically overestimates the loss of connectors and splices within the link.

a. True
b. False

Answer 19

b. False

p 11-20

For multimode applications, an OTDR typically underestimates the loss of connectors and splices within the link because it might have an under-filled launch; however, it can be used to characterize each element and evaluate consistency

Question 20

When the insertion loss is less than 3 dB at the frequency point where the measurement is made, the return loss measurement is ignored and not evaluated against the selected test limit/cabling standard.

a. True
b. False

Answer 20

a. True

p 11-5

This is often referred to as the 3 dB rule.

Question 21

When testing optical fiber cabling with an OTDR, the trace forms a line with a negative slope from left to right. Lower/shorter wavelengths have a ___ slope.

a. Shallower
b. Steeper

Answer 21

b. Steeper

p 11-21

Lower/shorter wavelengths (e.g., 850 nm) have a steeper slope.

Question 22

When testing balanced twisted-pair cabling, _____ is used as a requirement for applications that communicate over multiple pairs at the same time.

a. Power sum delay skew
b. Power sum return loss
c. Power sum insertion loss
d. Power sum crosstalk

Answer 22

d. Power sum crosstalk

p 11-7

Power sum crosstalk is used as a requirement for applications that communicate over multiple pairs at the same time.

Both NEXT and ACR-F can be specified as a power sum since the receive pair could have simultaneous crosstalk from the three other pairs (see Figure 11.7).

Question 23

When testing optical fiber cabling, attenuation measurements using an OLTS are determined according to the reference method used during setup. Uncertainty analysis has determined that the _____ reference method has a lower uncertainty than the other methods.

a. Two-jumper
b. One-jumper
c. Three-jumper

Answer 23

b. One-jumper

p 11-22

Uncertainty analysis has determined that the one-jumper reference method has a lower uncertainty than the other methods.

Question 24

The OTDR complements an OLTS by providing information that an OLTS cannot find, such as the ___, a good indicator of potential trouble.

a. Fault of the cable
b. Attenuation uniformity
c. Reflectance of a connector
d. Polarity of the cable

Answer 24

c. Reflectance of a connector

p 11-22

The OTDR complements an OLTS by providing information that an OLTS cannot find, such as the reflectance of a connector, a good indicator of potential trouble.

Question 25

A TDR method used to calculate the length of a balanced twisted-pair cable measures the time it takes a pulse to travel down the cable and back (called the round trip delay). This time is twice the ___.

a. Channel delay
b. Path delay
c. Propagation delay

Answer 25

c. Propagation delay

p 11-3

This time is twice the propagation delay. Pass/fail criteria are based on the maximum length allowed for the channel or permanent link plus the NVP uncertainty of 10 percent.

Question 26

Three configurations are defined for field testing horizontal balanced twisted-pair cabling. Which one of the following is not one of them?

a. End-to-end
b. Permanent link
c. MPTL
d. Channel

Answer 26

a. End-to-end

p 11-11

Three configurations are defined for field testing horizontal balanced twisted-pair cabling: a channel, a permanent link, and an MPTL.

Question 27

Insertion loss deviation is required as an acceptance test for balanced twisted-pair cabling.

a. True
b. False

Answer 27

b. False

p 11-5

Insertion loss deviation is not required as an acceptance test for balanced twisted-pair cabling.

Question 28

What is the worst case acceptance value for attenuation when testing 2000 m (6562 ft) of 50/125 multimode fiber at a wavelength of 1300 nm when the fiber has 2 connector pairs and 3 splices?

a. 3.4 dB
b. 4.65 dB
c. 5.4 dB
d. 6.4 dB

Answer 28

c. 5.4 dB

p 6-79

Question 29

Where backbone cabling exceeds cabling lengths for the same performance or design (for product used in horizontal cabling), there are three fundamental tests which should be considered when testing. They are:

a. Insertion loss (attenuation), return loss, and wiremap/strand identification
b. Insertion loss (attenuation), return loss, and continuity
c. Insertion loss (attenuation), return loss, and length
d. Insertion loss (attenuation), continuity, and wiremap/strand identification

Answer 29

d. Insertion loss (attenuation), continuity, and wiremap/strand identification

Question 30

You are preparing to test newly installed open office cabling. Within the open office cabling, there are multiple consolidation points (CP) that were installed while waiting for furniture. How do you proceed with permanent link testing?

a. Test to each CP, then test from CP to workstation.
b. Wait for open office cabling to be completed, then test to each workstation outlet, including the CP.
c. Test that the CP is within 90 meters, then test again to the workstation outlet.
d. Perform permanent link tests to each CP, then continuity tests from CP to each workstation outlet

Answer 30

b. Wait for open office cabling to be completed, then test to each workstation outlet, including the CP.

Question 31

Assume the following:
- An equipment room (ER) consists of 16 racks arranged in 4 equal rows
- The first 4 racks are numbered R1-1 though R1-4
- The second 4 racks are numbered R2-1 through R2-4
- A new equipment shelf with 12 slots is to be installed in the bottom of the third rack in the second row
- Each slot has 2 ports
What would be the identifier of the two ports on the eighth slot of the new equipment shelf?

a. R2-3-2-8-1 and R2-3-2-8-2
b. R3-2-2-8-1 and R3-2-2-8-2
c. R2-3-2-12-1 and R2-3-2-12-2
d. R3-2-2-12-1 and R3-2-2-12-2

Answer 31

a. R2-3-2-8-1 and R2-3-2-8-2

Question 32

You have been asked to test and troubleshoot an installed base of cabling that is believed to be causing network problems. You are finding that there are high levels of return loss upon initial testing. What testing will best determine the reasons for these failures?

a. Power meter
b. Continuity testing
c. Level II testing
d. Time domain reflectometer (TDR)

Answer 32

d. Time domain reflectometer (TDR)