Telecommunications Fiber Optics 1 — Questions and Answers
Question 1: What physical phenomenon allows fiber optic cables to transmit light?
- Reflection
- Total internal reflection (Correct answer)
- Refraction
- Diffraction
Correct answer: Total internal reflection
Total internal reflection causes light to bounce within the fiber core when it strikes the cladding at an angle below the critical angle.
Question 2: What is the difference between single-mode and multimode fiber?
- Single-mode is cheaper; multimode is more expensive
- Single-mode has a smaller core and supports longer distances; multimode has a larger core for shorter distances (Correct answer)
- Single-mode supports more wavelengths; multimode supports only one
- Single-mode is for copper; multimode is for glass
Correct answer: Single-mode has a smaller core and supports longer distances; multimode has a larger core for shorter distances
Single-mode fiber's smaller core (8-10 µm) allows only one light path, reducing dispersion and enabling longer transmission distances than multimode.
Question 3: What does OTDR stand for and what is it used for?
- Optical Time Domain Reflectometer; used to test fiber for faults and measure length (Correct answer)
- Optical Transmission Data Recorder; used to log network traffic
- Output Transfer Data Rate; used to measure bandwidth
- Optical Terminal Device Router; used to connect fiber to switches
Correct answer: Optical Time Domain Reflectometer; used to test fiber for faults and measure length
An OTDR (Optical Time Domain Reflectometer) sends light pulses into fiber and analyzes reflections to locate faults, splices, and measure cable length.
Question 4: What wavelength does standard single-mode fiber primarily use for long-haul transmission?
- 850 nm
- 1310 nm
- 1550 nm (Correct answer)
- 1625 nm
Correct answer: 1550 nm
1550 nm (C-band) is the preferred wavelength for long-haul single-mode transmission because optical fiber has minimum attenuation at this wavelength.
Question 5: What does WDM stand for in fiber optics?
- Wideband Data Multiplexing
- Wavelength Division Multiplexing (Correct answer)
- Wireless Data Management
- Waveguide Dense Modulation
Correct answer: Wavelength Division Multiplexing
WDM (Wavelength Division Multiplexing) combines multiple optical signals at different wavelengths on a single fiber, multiplying capacity.
Question 6: What causes chromatic dispersion in fiber optic cables?
- Physical bending of the fiber
- Different wavelengths traveling at slightly different speeds (Correct answer)
- Moisture penetration into the cladding
- Connector contamination
Correct answer: Different wavelengths traveling at slightly different speeds
Chromatic dispersion occurs because different wavelengths of light travel at slightly different velocities in the fiber, causing pulse broadening.
Telecommunications Fiber Optics 1
What physical phenomenon allows fiber optic cables to transmit light?