Certified Fiber Optic Technician (CFOT) Exam 100 Practice
Questions And Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. What does “attenuation” refer to in fiber optics?
a. Increase in signal power
b. Reflection of light at connectors
c. Loss of optical signal strength
d. Light traveling at different speeds
Rationale: Attenuation is the reduction of signal strength as light travels
through the fiber.
2. What is the primary function of the core in an optical fiber?
,a. Provide mechanical strength
b. Guide the light signal
c. Protect against moisture
d. Reflect external light
Rationale: Light travels through the core, which acts as the signal
pathway.
3. Which layer surrounds the core and keeps light inside?
a. Jacket
b. Strength members
c. Cladding
d. Buffer coating
Rationale: The cladding provides lower refractive index and keeps light
contained via total internal reflection.
4. What does “numerical aperture” determine?
a. Fiber bend radius
b. Light-gathering ability of the fiber
c. Signal wavelength
d. Fiber tensile strength
Rationale: NA measures the acceptance angle and how much light the
fiber can collect.
,5. Multimode fiber typically uses what core size?
a. 9 microns
b. 50 or 62.5 microns
c. 100 microns
d. 125 microns
Rationale: Multimode fibers have larger cores (50/125 or 62.5/125).
6. Single-mode fiber is mainly used for:
a. Short LAN networks
b. Broadcast CATV only
c. Long-distance, high-bandwidth communication
d. Military tactical systems
Rationale: Single-mode supports long-distance transmission with minimal
dispersion.
7. What is the primary cause of dispersion in multimode fiber?
a. Thermal expansion
b. Multiple light paths
c. Fiber stretching
d. UV exposure
, Rationale: Multimode fibers allow many propagation modes that arrive at
different times.
8. Which wavelength is most commonly used in single-mode systems?
a. 660 nm
b. 850 nm
c. 900 nm
d. 1310 nm or 1550 nm
Rationale: SM systems operate mainly at 1310 nm and 1550 nm.
9. What is the function of strength members in a fiber cable?
a. Carry the optical signal
b. Provide tensile support
c. Block moisture
d. Improve dispersion
Rationale: Strength members protect the fiber from pulling forces.
10. The minimum bend radius is usually specified to prevent:
a. Chromatic dispersion
b. Electromagnetic interference
c. Excessive signal loss and fiber damage
Questions And Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. What does “attenuation” refer to in fiber optics?
a. Increase in signal power
b. Reflection of light at connectors
c. Loss of optical signal strength
d. Light traveling at different speeds
Rationale: Attenuation is the reduction of signal strength as light travels
through the fiber.
2. What is the primary function of the core in an optical fiber?
,a. Provide mechanical strength
b. Guide the light signal
c. Protect against moisture
d. Reflect external light
Rationale: Light travels through the core, which acts as the signal
pathway.
3. Which layer surrounds the core and keeps light inside?
a. Jacket
b. Strength members
c. Cladding
d. Buffer coating
Rationale: The cladding provides lower refractive index and keeps light
contained via total internal reflection.
4. What does “numerical aperture” determine?
a. Fiber bend radius
b. Light-gathering ability of the fiber
c. Signal wavelength
d. Fiber tensile strength
Rationale: NA measures the acceptance angle and how much light the
fiber can collect.
,5. Multimode fiber typically uses what core size?
a. 9 microns
b. 50 or 62.5 microns
c. 100 microns
d. 125 microns
Rationale: Multimode fibers have larger cores (50/125 or 62.5/125).
6. Single-mode fiber is mainly used for:
a. Short LAN networks
b. Broadcast CATV only
c. Long-distance, high-bandwidth communication
d. Military tactical systems
Rationale: Single-mode supports long-distance transmission with minimal
dispersion.
7. What is the primary cause of dispersion in multimode fiber?
a. Thermal expansion
b. Multiple light paths
c. Fiber stretching
d. UV exposure
, Rationale: Multimode fibers allow many propagation modes that arrive at
different times.
8. Which wavelength is most commonly used in single-mode systems?
a. 660 nm
b. 850 nm
c. 900 nm
d. 1310 nm or 1550 nm
Rationale: SM systems operate mainly at 1310 nm and 1550 nm.
9. What is the function of strength members in a fiber cable?
a. Carry the optical signal
b. Provide tensile support
c. Block moisture
d. Improve dispersion
Rationale: Strength members protect the fiber from pulling forces.
10. The minimum bend radius is usually specified to prevent:
a. Chromatic dispersion
b. Electromagnetic interference
c. Excessive signal loss and fiber damage
