CFOT Fiber Optic System Components and Equipment 2 — Questions and Answers
Question 1: What is an optical attenuator used for in a fiber optic link?
- Reduce optical power to prevent receiver saturation (Correct answer)
- Increase signal strength at the transmitter
- Filter out specific wavelengths of light
- Measure optical return loss
Correct answer: Reduce optical power to prevent receiver saturation
Optical attenuators intentionally reduce signal power to prevent overloading a receiver when the transmitted power exceeds the receiver's dynamic range.
Question 2: A fiber optic patch panel in a telecommunications room primarily serves what function?
- Provide a flexible cross-connect point between backbone and horizontal cabling (Correct answer)
- Amplify fiber optic signals between floors
- Terminate outdoor armored cables and protect from moisture
- Store excess fiber slack in organized loops
Correct answer: Provide a flexible cross-connect point between backbone and horizontal cabling
Patch panels provide a centralized, organized cross-connect interface where technicians can reroute connections using patch cords without disturbing permanent cabling.
Question 3: What is the difference between a simplex and a duplex fiber optic cable assembly?
- Simplex has one fiber; duplex has two fibers in one jacket for separate TX and RX paths (Correct answer)
- Simplex uses single-mode; duplex uses multimode
- Simplex transmits in both directions; duplex transmits in one direction only
- Simplex is for inside plant; duplex is for outside plant use
Correct answer: Simplex has one fiber; duplex has two fibers in one jacket for separate TX and RX paths
A simplex assembly contains one fiber for one-way transmission, while a duplex assembly contains two fibers allowing separate transmit and receive paths.
Question 4: In DWDM systems, what is the typical channel spacing defined by the ITU-T G.694.1 grid?
- 100 GHz (approximately 0.8 nm) or 50 GHz (approximately 0.4 nm) (Correct answer)
- 1 nm or 2 nm
- 10 nm or 20 nm
- 200 GHz or 400 GHz only
Correct answer: 100 GHz (approximately 0.8 nm) or 50 GHz (approximately 0.4 nm)
ITU-T G.694.1 defines the DWDM frequency grid with standard spacings of 100 GHz (~0.8 nm) and 50 GHz (~0.4 nm) in the C-band.
Question 5: What is the function of a fiber optic isolator in a laser transmitter circuit?
- Prevent back-reflected light from entering and destabilizing the laser source (Correct answer)
- Increase laser output power
- Split the laser output into equal portions for monitoring
- Convert the laser beam from free-space to guided fiber
Correct answer: Prevent back-reflected light from entering and destabilizing the laser source
Optical isolators allow light to pass in only one direction, blocking back-reflections that would cause laser instability, noise, or damage.
Question 6: What component in a fiber optic receiver converts incoming optical signals into electrical signals?
- Photodetector (PIN diode or avalanche photodiode) (Correct answer)
- Optical amplifier (EDFA)
- Modulator (Mach-Zehnder)
- Wavelength locker
Correct answer: Photodetector (PIN diode or avalanche photodiode)
The photodetector (typically a PIN diode or APD) performs O/E conversion by generating an electrical current proportional to the incident optical power.
CFOT Fiber Optic System Components and Equipment 2
What is an optical attenuator used for in a fiber optic link?