CTE CTE Fiber Optics & Transmission Systems

Question 1

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

Accepted Answer

0.2 dB/km

Answer

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.

Question 2

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

Accepted Answer

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

Answer

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.

Question 3

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

Accepted Answer

Chromatic dispersion

Answer

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

Question 4

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

Accepted Answer

A mechanical connector or reflective splice

Answer

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

Question 5

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

Accepted Answer

ITU-T G.694.1

Answer

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.

CTE - Certified Telecommunications Engineer Practice Test

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CTE CTE Fiber Optics & Transmission Systems