CO Fiber Optic Installer Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
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1. What is the primary function of the core in a fiber-optic cable?
A. Provide mechanical protection
B. Carry the optical signal
C. Prevent moisture intrusion
D. Provide electrical grounding
Answer: B. Carry the optical signal
Rationale: The core is the central light-carrying region of an optical
fiber. It is surrounded by cladding, which has a lower refractive index
and keeps light confined within the core through total internal
reflection.
2. Which principle allows light to remain confined within an optical
fiber?
,A. Electromagnetic induction
B. Total internal reflection
C. Magnetic flux
D. Electrical capacitance
Answer: B. Total internal reflection
Rationale: Total internal reflection occurs when light traveling
through a higher-index medium reaches a boundary with a lower-
index medium at an appropriate angle. This principle allows optical
signals to travel through the fiber core with relatively low loss.
3. Which type of fiber generally has a larger core diameter?
A. Single-mode fiber
B. Multimode fiber
C. Polarization-maintaining fiber
D. Dispersion-compensating fiber
Answer: B. Multimode fiber
Rationale: Multimode fiber typically has a larger core, commonly 50
or 62.5 micrometers, compared with the approximately 8–10
micrometer core of single-mode fiber. The larger core permits multiple
propagation modes.
4. What is a typical core diameter of single-mode fiber?
,A. 8–10 µm
B. 25 µm
C. 50–62.5 µm
D. 125 µm
Answer: A. 8–10 µm
Rationale: Standard single-mode fiber has a very small core, generally
around 8–10 micrometers in diameter. The overall glass cladding is
typically 125 micrometers in diameter.
5. Which wavelength is commonly used for long-distance single-
mode fiber transmission?
A. 650 nm
B. 850 nm
C. 1310 nm
D. 455 nm
Answer: C. 1310 nm
Rationale: 1310 nm is a major telecommunications wavelength for
single-mode fiber and has relatively low chromatic dispersion in
standard single-mode fiber. Other important telecommunications
wavelengths include 1550 nm and 1625 nm.
, 6. Which wavelength is commonly associated with multimode fiber
systems?
A. 850 nm
B. 1310 GHz
C. 1550 GHz
D. 1625 GHz
Answer: A. 850 nm
Rationale: 850 nm is widely used with multimode fiber, particularly
with short-reach data communications systems. The wavelength is
compatible with common VCSEL-based transceivers.
7. What does attenuation describe in a fiber-optic system?
A. Increase in optical power
B. Loss of optical power as light travels through the fiber
C. Increase in cable diameter
D. Change in connector color
Answer: B. Loss of optical power as light travels through the fiber
Rationale: Attenuation is the reduction of optical signal power as it
travels through a fiber or passive component. It is normally expressed
in decibels per kilometer (dB/km) for fiber.
8. Which unit is commonly used to express fiber attenuation?
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary function of the core in a fiber-optic cable?
A. Provide mechanical protection
B. Carry the optical signal
C. Prevent moisture intrusion
D. Provide electrical grounding
Answer: B. Carry the optical signal
Rationale: The core is the central light-carrying region of an optical
fiber. It is surrounded by cladding, which has a lower refractive index
and keeps light confined within the core through total internal
reflection.
2. Which principle allows light to remain confined within an optical
fiber?
,A. Electromagnetic induction
B. Total internal reflection
C. Magnetic flux
D. Electrical capacitance
Answer: B. Total internal reflection
Rationale: Total internal reflection occurs when light traveling
through a higher-index medium reaches a boundary with a lower-
index medium at an appropriate angle. This principle allows optical
signals to travel through the fiber core with relatively low loss.
3. Which type of fiber generally has a larger core diameter?
A. Single-mode fiber
B. Multimode fiber
C. Polarization-maintaining fiber
D. Dispersion-compensating fiber
Answer: B. Multimode fiber
Rationale: Multimode fiber typically has a larger core, commonly 50
or 62.5 micrometers, compared with the approximately 8–10
micrometer core of single-mode fiber. The larger core permits multiple
propagation modes.
4. What is a typical core diameter of single-mode fiber?
,A. 8–10 µm
B. 25 µm
C. 50–62.5 µm
D. 125 µm
Answer: A. 8–10 µm
Rationale: Standard single-mode fiber has a very small core, generally
around 8–10 micrometers in diameter. The overall glass cladding is
typically 125 micrometers in diameter.
5. Which wavelength is commonly used for long-distance single-
mode fiber transmission?
A. 650 nm
B. 850 nm
C. 1310 nm
D. 455 nm
Answer: C. 1310 nm
Rationale: 1310 nm is a major telecommunications wavelength for
single-mode fiber and has relatively low chromatic dispersion in
standard single-mode fiber. Other important telecommunications
wavelengths include 1550 nm and 1625 nm.
, 6. Which wavelength is commonly associated with multimode fiber
systems?
A. 850 nm
B. 1310 GHz
C. 1550 GHz
D. 1625 GHz
Answer: A. 850 nm
Rationale: 850 nm is widely used with multimode fiber, particularly
with short-reach data communications systems. The wavelength is
compatible with common VCSEL-based transceivers.
7. What does attenuation describe in a fiber-optic system?
A. Increase in optical power
B. Loss of optical power as light travels through the fiber
C. Increase in cable diameter
D. Change in connector color
Answer: B. Loss of optical power as light travels through the fiber
Rationale: Attenuation is the reduction of optical signal power as it
travels through a fiber or passive component. It is normally expressed
in decibels per kilometer (dB/km) for fiber.
8. Which unit is commonly used to express fiber attenuation?
