BDS Fiber Optic Systems in HFC

Question 1

What does HFC stand for in cable network architecture?

Accepted Answer

Hybrid Fiber-Coaxial

Answer

HFC stands for Hybrid Fiber-Coaxial, describing a network architecture that uses fiber optic cable from the headend to neighborhood nodes and coaxial cable for the final distribution to homes.

Question 2

What is the function of an optical node in an HFC network?

Accepted Answer

It converts optical signals to RF signals (and vice versa) for distribution over coax

Answer

An optical node (fiber node) converts downstream optical signals from the headend into RF electrical signals for coaxial distribution, and converts upstream RF signals into optical signals for return to the headend.

Question 3

What type of laser is most commonly used in HFC headends for downstream optical transmission?

Accepted Answer

DFB (Distributed Feedback) laser

Answer

DFB (Distributed Feedback) lasers are used in HFC headends because their narrow spectral linewidth minimizes chromatic dispersion and clipping distortion over long fiber runs.

Question 4

What is optical clipping distortion in an HFC transmitter?

Accepted Answer

Distortion caused when the optical modulation drives the laser below its lasing threshold, clipping the signal waveform

Answer

Optical clipping occurs when high composite RF input power drives the laser into its sub-threshold region, causing the negative peaks of the signal to be clipped and generating significant distortion.

Question 5

What is the purpose of an optical attenuator in an HFC fiber link?

Accepted Answer

To reduce optical power to an acceptable receive level and prevent photodetector saturation

Answer

An optical attenuator reduces optical power in a fiber link to prevent the receiver photodetector from being saturated by excessive signal levels, which would cause distortion and errors.

BDS - Broadband Distribution Specialist Practice Test

BDS - Broadband Distribution Specialist Practice Test

BDS Fiber Optic Systems in HFC