NCTI Fiber Testing & Maintenance Certification Exam With
Correct Solutions.
1. In an HFC (Hybrid Fiber-Coax) network, what is the primary function of the Optical Node?
Correct Answer The node converts downstream optical signals from the headend into RF
electrical signals for the coaxial network, and converts upstream RF signals into optical
signals for return.
2. When using an OTDR, what setting must be manually entered to ensure the device calculates
the physical distance to a break accurately based on the speed of light in that specific glass?
Correct Answer The Index of Refraction (IOR).
3. What is the maximum allowable loss for a single mated connector pair according to TIA/EIA-
568 standards often used in NCTI training?
Correct Answer 0.75 dB.
4. During a "Link Loss Budget" calculation, if you have a 10km run of G.652 fiber at 1310nm
(0.35 dB/km) with two connectors (0.5 dB each) and four splices (0.1 dB each), what is the
total estimated loss?
Correct Answer 4.9 dB.
5. Why is 1550nm typically used for long-haul transport and video overlay in cable networks
rather than 1310nm?
Correct Answer 1550nm has lower attenuation (approx. 0.22 dB/km) and is compatible with
Erbium-Doped Fiber Amplifiers (EDFAs).
6. What phenomenon occurs when light hits the boundary between the core and the cladding
at a shallow angle and is reflected back into the core?
Correct Answer Total Internal Reflection.
7. In a PON (Passive Optical Network), what device is used to split a single fiber from the OLT to
serve up to 32 or 64 individual subscribers?
Correct Answer An Optical Splitter.
8. When troubleshooting with a Visual Fault Locator (VFL), a red glow visible through a yellow
jumper jacket usually indicates what?
Correct Answer A macrobend, a break, or a severe pinch in the fiber.
9. Why is "99% Isopropyl Alcohol" required for cleaning fiber instead of standard "70% Rubbing
Alcohol"?
Correct Answer 70% alcohol contains water and oils that leave a residue or film on the fiber
end-face, which increases signal loss.
10. What is the standard diameter of the cladding for both single-mode and multimode optical
fibers?
Correct Answer 125 microns.
, 11. Describe the "Event Dead Zone" on an OTDR trace.
Correct Answer It is the minimum distance after a reflective event (like a connector) where
the OTDR can distinguish the next event.
12. What does "APC" stand for, and what color is the connector housing?
Correct Answer Angled Physical Contact; Green.
13. Why are APC connectors used in CATV/Video systems instead of UPC connectors?
Correct Answer The 8-degree angle causes reflections to leak into the cladding, providing
higher Return Loss (>60dB), which prevents "ghosting" in video signals.
14. What is "Rayleigh Scattering"?
Correct Answer The natural, microscopic reflections caused by density variations in the glass;
this is the light the OTDR uses to measure attenuation.
15. What is the "Mode Field Diameter" (MFD) of a standard single-mode fiber?
Correct Answer Approximately 9 to 10 microns.
16. In an OTDR trace, what is a "Gainer"?
Correct Answer An apparent (but false) gain in signal at a splice point caused by a mismatch
in backscatter coefficients between two fibers.
17. What is "Macrobending"?
Correct Answer A large-scale bend in the fiber (visible to the eye) that exceeds the minimum
bend radius and causes light to leak out of the core.
18. What is the purpose of the "Aramid Yarn" (Kevlar) in a fiber optic cable?
Correct Answer To provide tensile strength and protect the glass from being stretched during
installation.
19. Which wavelength is most sensitive to bending loss and is often used to detect "pinches" in a
splice tray?
Correct Answer 1550nm (or 1625nm).
20. What is the role of an "Optical Attenuator"?
Correct Answer To reduce the optical power to a specific level to avoid saturating or
damaging a receiver.
21. What does "dBm" represent in fiber testing?
Correct Answer Absolute power referenced to 1 milliwatt.
22. If a power meter reads -3 dBm and then drops to -6 dBm, how much of the optical power has
been lost?
Correct Answer 50% (A 3dB drop always represents a 50% loss in power).
23. What is "Chromatic Dispersion"?
Correct Solutions.
1. In an HFC (Hybrid Fiber-Coax) network, what is the primary function of the Optical Node?
Correct Answer The node converts downstream optical signals from the headend into RF
electrical signals for the coaxial network, and converts upstream RF signals into optical
signals for return.
2. When using an OTDR, what setting must be manually entered to ensure the device calculates
the physical distance to a break accurately based on the speed of light in that specific glass?
Correct Answer The Index of Refraction (IOR).
3. What is the maximum allowable loss for a single mated connector pair according to TIA/EIA-
568 standards often used in NCTI training?
Correct Answer 0.75 dB.
4. During a "Link Loss Budget" calculation, if you have a 10km run of G.652 fiber at 1310nm
(0.35 dB/km) with two connectors (0.5 dB each) and four splices (0.1 dB each), what is the
total estimated loss?
Correct Answer 4.9 dB.
5. Why is 1550nm typically used for long-haul transport and video overlay in cable networks
rather than 1310nm?
Correct Answer 1550nm has lower attenuation (approx. 0.22 dB/km) and is compatible with
Erbium-Doped Fiber Amplifiers (EDFAs).
6. What phenomenon occurs when light hits the boundary between the core and the cladding
at a shallow angle and is reflected back into the core?
Correct Answer Total Internal Reflection.
7. In a PON (Passive Optical Network), what device is used to split a single fiber from the OLT to
serve up to 32 or 64 individual subscribers?
Correct Answer An Optical Splitter.
8. When troubleshooting with a Visual Fault Locator (VFL), a red glow visible through a yellow
jumper jacket usually indicates what?
Correct Answer A macrobend, a break, or a severe pinch in the fiber.
9. Why is "99% Isopropyl Alcohol" required for cleaning fiber instead of standard "70% Rubbing
Alcohol"?
Correct Answer 70% alcohol contains water and oils that leave a residue or film on the fiber
end-face, which increases signal loss.
10. What is the standard diameter of the cladding for both single-mode and multimode optical
fibers?
Correct Answer 125 microns.
, 11. Describe the "Event Dead Zone" on an OTDR trace.
Correct Answer It is the minimum distance after a reflective event (like a connector) where
the OTDR can distinguish the next event.
12. What does "APC" stand for, and what color is the connector housing?
Correct Answer Angled Physical Contact; Green.
13. Why are APC connectors used in CATV/Video systems instead of UPC connectors?
Correct Answer The 8-degree angle causes reflections to leak into the cladding, providing
higher Return Loss (>60dB), which prevents "ghosting" in video signals.
14. What is "Rayleigh Scattering"?
Correct Answer The natural, microscopic reflections caused by density variations in the glass;
this is the light the OTDR uses to measure attenuation.
15. What is the "Mode Field Diameter" (MFD) of a standard single-mode fiber?
Correct Answer Approximately 9 to 10 microns.
16. In an OTDR trace, what is a "Gainer"?
Correct Answer An apparent (but false) gain in signal at a splice point caused by a mismatch
in backscatter coefficients between two fibers.
17. What is "Macrobending"?
Correct Answer A large-scale bend in the fiber (visible to the eye) that exceeds the minimum
bend radius and causes light to leak out of the core.
18. What is the purpose of the "Aramid Yarn" (Kevlar) in a fiber optic cable?
Correct Answer To provide tensile strength and protect the glass from being stretched during
installation.
19. Which wavelength is most sensitive to bending loss and is often used to detect "pinches" in a
splice tray?
Correct Answer 1550nm (or 1625nm).
20. What is the role of an "Optical Attenuator"?
Correct Answer To reduce the optical power to a specific level to avoid saturating or
damaging a receiver.
21. What does "dBm" represent in fiber testing?
Correct Answer Absolute power referenced to 1 milliwatt.
22. If a power meter reads -3 dBm and then drops to -6 dBm, how much of the optical power has
been lost?
Correct Answer 50% (A 3dB drop always represents a 50% loss in power).
23. What is "Chromatic Dispersion"?
