BDS Network Testing and Measurement

Question 1

What instrument does a cable technician primarily use to measure downstream signal levels in the HFC plant?

Accepted Answer

Signal level meter (field analyzer)

Answer

Digital voltmeter

Answer

Spectrum analyzer only

Answer

OTDR

Question 2

What does a spectrum analyzer display when used on a cable plant?

Accepted Answer

A frequency-domain plot showing signal amplitude versus frequency across the spectrum

Answer

A time-domain plot of signal voltage versus time

Answer

A constellation diagram of a single QAM channel

Answer

A list of all active DOCSIS modems on the node

Question 3

What is a QAM analyzer used for in field testing?

Accepted Answer

To demodulate and analyze a specific QAM channel, displaying MER, BER, constellation diagram, and error counts

Answer

To measure optical power in fiber nodes

Answer

To generate QAM test signals for alignment

Answer

To monitor all upstream channels simultaneously from a node port

Question 4

What does a cable technician measure to evaluate the quality of the upstream path at a node test point?

Accepted Answer

Upstream noise floor, ingress signals, and upstream modem transmit levels using a return-path sweep or spectrum analyzer

Answer

Downstream carrier levels only

Answer

The node's optical receive power

Answer

The downstream tilt across the node service area

Question 5

What is the purpose of a TDR (Time Domain Reflectometer) in cable plant maintenance?

Accepted Answer

To locate cable faults (breaks, shorts, impedance changes) by sending a pulse into the coax and measuring the time for reflections to return

Answer

To measure optical signal loss in fiber spans

Answer

To align amplifier output levels

Answer

To test cable modem upstream transmit power

Question 6

What does a 'sweep' test measure in an HFC plant?

Accepted Answer

The frequency response (amplitude vs. frequency) of a cable segment by injecting test tones and measuring the received levels at the far end

Answer

The number of active subscribers on a node

Answer

The upstream noise level at the headend

Answer

The optical power budget from headend to node