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Fiber Optics & Physical Layer Technologies Flashcards

6 cards from real CTA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the primary difference between single-mode fiber (SMF) and multimode fiber (MMF)?

    Answer: SMF has a smaller core that supports one light path, enabling longer distances; MMF has a larger core supporting multiple light paths over shorter distances

    Single-mode fiber's narrow core (~9 µm) allows only one propagation mode, minimizing dispersion and enabling distances of hundreds of kilometers, while multimode fiber's wider core (~50–62.5 µm) supports shorter enterprise runs.

  2. What phenomenon in fiber optic transmission causes different wavelengths of light to travel at slightly different speeds, limiting bandwidth over distance?

    Answer: Chromatic dispersion

    Chromatic dispersion occurs because different wavelengths travel at different speeds in glass, causing pulse spreading that limits high-speed transmission over long distances.

  3. In DWDM (Dense Wavelength Division Multiplexing), what is the standard channel spacing defined by the ITU-T grid?

    Answer: 100 GHz (approximately 0.8 nm)

    The ITU-T G.694.1 standard defines DWDM channel spacing at 100 GHz (or 50 GHz for denser grids), allowing many wavelengths to be transmitted simultaneously on one fiber.

  4. What type of fiber connector is most commonly used in US data centers and enterprise networks for high-density single-mode applications?

    Answer: LC (Lucent Connector)

    The LC connector's small form factor makes it the dominant choice for high-density data center and enterprise applications with both single-mode and multimode fiber.

  5. What does an OTDR (Optical Time-Domain Reflectometer) measure in a fiber optic link?

    Answer: The distance to faults, splices, and connectors by analyzing backscattered light pulses

    An OTDR sends light pulses into a fiber and analyzes the reflections and backscatter to locate and characterize faults, connectors, and splices along the link.

  6. What is the typical operating wavelength window for long-haul single-mode fiber transmission in DWDM systems?

    Answer: 1550 nm C-band (approximately 1530–1565 nm)

    The C-band (around 1550 nm) provides the lowest attenuation in standard single-mode fiber and is the primary window for long-haul DWDM transmission.