CTE Fiber Optics & Transmission Systems Flashcards

What is the maximum attenuation typically specified for single-mode fiber at 1550 nm in modern DWDM systems?

Answer: 0.2 dB/km

Modern single-mode fiber (ITU-T G.652) exhibits approximately 0.2 dB/km attenuation at the 1550 nm transmission window used by DWDM systems.

What distinguishes single-mode fiber (SMF) from multimode fiber (MMF) in terms of core diameter?

Answer: SMF has a ~9 µm core; MMF has a 50–62.5 µm core

Single-mode fiber has a ~9 µm core that supports only one propagation mode, while multimode fiber has a 50 or 62.5 µm core supporting many modes.

What type of dispersion in single-mode fiber causes different wavelength components of a pulse to travel at different speeds?

Answer: Chromatic dispersion

Chromatic dispersion (comprising material and waveguide dispersion) causes wavelengths to propagate at different group velocities, broadening the pulse over distance.

In an OTDR trace, a sharp spike followed by a loss step typically indicates what type of event?

Answer: A mechanical connector or reflective splice

Mechanical connectors and air-gap splices cause Fresnel reflection (the spike) plus insertion loss (the step) on an OTDR trace.

Which ITU-T recommendation defines Dense Wavelength Division Multiplexing (DWDM) channel spacing and frequency grid?

Answer: ITU-T G.694.1

ITU-T G.694.1 defines the DWDM frequency grid with nominal central frequencies and channel spacings of 12.5, 25, 50, or 100 GHz.

What is the primary function of an Erbium-Doped Fiber Amplifier (EDFA) in a long-haul DWDM link?

Answer: Amplify multiple WDM channels simultaneously in the optical domain without O-E-O conversion

An EDFA boosts all WDM channels simultaneously in the C-band (1530–1565 nm) optically, avoiding costly per-channel electrical regeneration.