Test Help

1. The most common source of ingress and egress is located at which of the following points in the broadband cable network?

At the coax interface on the node.

At the headend.

The customer premises and the drop cable

At the distribution amplifier.

2. What type of digital modulation is specified in set-top box (STB) systems used in North America?

16-QAM (quadrature amplitude modulation).

Frequency shift keying (FSK).

Phase shift keying (PSK).

Quadrature phase shift keying (QPSK).

3. Which of the following procedures will reduce Impulse noise?

Impulse noise can be reduced by locating taps and splitters close to switching powersupplies.

Impulse noise can be reduced by tightening all connections and installing 75omb terminators on unused taps.

Impulse noise can be reduced by transmitting power on the distribution amplifiers.

4. What are some possible causes of signal reflections?

Unpowered house amplifiers that reflect signals back to their source.

Loose or bad connections at the tap or nonterminated splitter ports in the drop system.

The use of splitters instead of directional couplers in the drop system.

Overloaded input levels to a house amplifier that are reflected back to their source.

5. What are the standard wavelengths for fiber-optic communications systems?

700 nm, 1,300 nm, 1,550 nm, and 1,625 nm.

380 nm, 700 nm, 1,550 nm, and 1,625 nm.

850 nm, 1,300 nm, 1,550' nm, and 1,625 nm

380 nm, 1,300 nm, 1,550, and 1,625 nm.

6. After common path distortion (CPD) or digital-CPD (D-CPD) has been identified and isolated to a single drop system, what is a practical resolution tactic to avoid customer frustration?

Replace the drop cable fr~e lap to the customer premises following current standardsfor weather protection.

Install drip loops below every connection exposed to weather elements to prevent water migration into the connections.

7. If the drop loss at the ground block is 3.2 dB and is connected to a thlee-way splitter's hot leg and then connected to the 9 dB leg of a directional coupler (DC), what will be the total return path loss?

8. What might be associated with a cable modem termination system (CMTS) input port with too high of an attenuator pad installed?

A high percentage of cable modems are transmitting at their maximum output level.

The output levels from the return amplifiers are 3 dB low.

The cable modems are operating fine, but the set-top boxes (STB) are not responding to polls.

A high percentage of cable modems are transmitting at their minimum output level

9. When the noise power ratio (NPR) of a laser is plotted on a chart, what happens when the maximum input power to the laser is reached?

The laser goes into nonlinear operation and the (NPR) drops off dramatically.

The laser goes into linear operation and the NPR drops off dramatically.

The laser goes into linear operation and the NPR improves dramatically.

The laser goes into nonlinear operation and the NPR improves dramatically.

10. What must be done before a cable modem emulater can be used to check the operations of a cable modem in the customer premises?

11. Which of the following should be added when compensating for tilt through a line extender?

Install a return equalizer closest to the value of the tilt.

Install a return equalizer 20 dB more than the value of the tilt.

Install a return equalizer half the value of the tilt.

Install a return equalizer double the value of the tilt.

12. What is common solution to impulse noise and ingress problems in the network where tap values are less than 14db?

Installing high-pass filters on all unused tap ports

Installing high-pass filters on tap ports that are 17 dB or less

Replacing tap plates of 17db or less with higher value tap plates

Installing terminators on all unused tap ports

13. What could be the cause of high 120 Hz hum measurement on a signal level meter (SLM)?

Hum at 120 Hz or higher is caused by too much current flowing through

Hum at 120 Hz or higher is caused by the filtering of the RF signal from an AC powersupply.

Hum at 120 Hz or higher is caused by poor filtering of the AC signal from a DC power supply.

14. Which of the following describes the primary source of attenuation in the return path?

Attenuation in the return path is primarily due to the passive devices.

Attenuation in the return path is primarily due to fiber-optic cable.

Attenuation in the return path is primarily due to the active devices.

Attenuation in the return path is primarily due to the coaxial cable

15. When aligning the return path through an unfamiliar amplifier module why is it a good practice to examine the amplifier module's block diagram before injecting test carriers?

To determine the gain of the amplifier installed in the return section of the amplifier module.

To determine the signal flow through the amplifier module and to identify where to inject the test carriers.

To determine the type of mechanism used to direct signal flow through the amplifiermodule.

To determine what value attenuator pad and equalizer should be installed in the returnsection of the amplifier module.

16. How does the media access control (MAC) in Data Over Cable Service Interface Specification (DOCSIS) version 1.1 and higher prevent packet delays in the transport of real-time applications?

The MAC sends a scouting message to determine the fastest and most direct routethrough the network for real-time applications.

17. Why is it necessary to balance each path separately,when balancing the return through a distribution amplifier?

Distribution amplifiers typically have multiple return paths coming from different nodes at different amplitude levels.

Distribution amplifiers typically have multiple return paths which may contain different amounts of attenuation.

Distribution amplifiers typically have multiple return paths which have dedicatedamplifiers for each path.

Distribution amplifiers typically have multiple return paths which contain equal amounts of attenuation.

18. Which of the following describes the typical sub-band return frequency design for a cable modem?

Most cable modems are configured to operate above 28 and below 38 MHz

Most cable modems are configured to operate above 5 and below 20 MHz

Most cable modems are configured to operate above 38 and below S4 MHz.

Most cable modems are configured to operate above 38 and below 42 MHz

19. How many bits of data can be transported in a 64-QAM carrier during a single clock cycle?

Eight bits of data representing the decimal values 0 through 63

Two bits of data representing the decimal values 0 through 63.

Six bits of data representing the decimal values 0 through 63.

Four bits of data representing the decimal values 1 through 63.

20. The use of a directional coupler requires which of the following adjustments in the return paths?

Each return amplifier must be adjusted by the decibel (dB) value of the directionalcoupler (DC).

Each return amplifier must be adjusted so that the levels received at the next amplifier are 25 dbmv.

21. Which of the following mitigation devices provide filtering on sub-split return frequencies as described?"

Window filters act on specific frequencies from 5-42 MHz

Window filters act on specific frequencies above 5-42 MHz

High-pass filters block all frequencies above 108 MHz

Step attenuators provide 100 dB of attenuation on frequencies from 5-42 MHz

22. Where should the sweep pulse be to avoid Interference with active services when weeping the return path?

Place the sweep pulses at the center frequency of each of the quadrature amplitudemodulation (QAM) carriers to avoid interference.

Place the sweep pulses 4.5 MHz above the center frequency of the quadrature amplitudemodulation (QAM) carriers to avoid interference.

Place the sweep pulses between the quadrature amplitude modulation (QAM) carriers toavoid interference.

23. Which of the following must be considered before selecting an amplitude level for the injected sweep carrier?

Consider the voltage at the power inserter test point

Consider any attenuation such as a splitter, that may exist between the signal level meter (SLM) and the test point.

Consider the output power of the laser and all Insertion losses in the path to the opticalpath to the headend.

Consider the amplitude of the input signal reaching the amplifier from all the customerpremises equipment (CPE).

24. What sampling rate should be used to convert the analog return path signal to a digital Signal?

25. What variables must be considered when designing combination of optical multiplexing techniques in the return path?

Service penetration, the density of the customer base, and the distance the return signals need to be carried

Service penetration, the density of the customer base, and the distance the forward signals need to be carried.

Service penetration, the affluence of the customer base, and the distance the returnsignals need to be carried

Service penetration, the density of the return channels, and the distance the returnsignals need to be carried

26. What should be checked in the drop system if the output level from a cable modem is relatively low (32 dBmv) and the output level from set-top boxes (STB) connected to four different outlets IS 60 DBmV (maximum output)?

27. Why must separate test carriers be injected into the return path when aligning the return amplifiers?

Because forward carriers are not always present making it difficult to measure carrierlevels in and out of a return amplifier.

Because return carriers only operate at 20 dBmV, repeat every 300 milliseconds and occupy 18 MHz

Because return carriers are always present making it difficult to measure carrier levels inand out of a return amplifier.

28. If a return path impairment appears to be caused by impulse nolse, why is it a good idea to begin trouble shooting at distribution taps of 17 dB or lower?

29. Which of the following best describes dense wavelength division multiplexing (DWDM)?

DWDM uses a multiplexer with a narrow range of wavelengths inside the C-band.

DWDM converts blocks of multiple return paths to higher frequency bands and sequentially stacks them on top of one another

DWDM provides only two optical channels in either the 1,310 or 1,550 nanometer (nm)light spectrum.

30. What is the purpose of the transceiver in a return path alignment and sweep system?

31. When setting up the reverse path through the optical network, when should the RF output level from the optical receiver be adjusted?

32. What must the technician calculate when the transceiver in the return path alignment system reports direct measurements to the signal level meter (SLM) in the field?

The technician must calculate the difference between the specified input to the transceiver and the measured input.

The technician must ca cu ate the bandwidth correction for a quadrature amplitudemodulation (QAM) carrier.

The technician must calculate the bandwidth correction for cumulative carriers beingreceived by the transceiver.

33. What did version 2.0 of the Data Over Cable service interface specification (DOCSIS) do to enable the use of higher orders of modulation and wider carrier bandwidth of the return carriers from cable modems?

34. How can the symbol rates of quadrature phase shift keying (QPSK) modulation be increased?

Increase the amplitude of the RF carrier.

Increase the number of bits per symbol from two to four.

Increase the RF transmission frequency.

Increase the RF bandwidth.

35. What should be done to maintain unity gain when a return amplifier has 20 dB of gain and the path attenuation at the output of the amplifier is 18 db ?

The output of the amplifier should be reduced by instaIIing a 2 dB attenuator pad to the amplifier's output.

Replace the internal amplifier stage with one that has only 18 dB of gain.

The output of the amplifier should be reduced by installing a 2 dB attenuator pad in the amplifier's input stage

36. How is optical demultiplexing achieved?

Optical demultiplexing requires a specialized receiver to convert all the optical wavelengths into a single RF channel

Optical demultiplexing uses fiber Bragg amplifiers to separate the different wavelengths of optical signals through an optical fiber.

Optical demultiplexing use optical filter to separate the different wavelengths of optical signals through an optical fiber

Optical demultiplexing uses optical splitters to feed a portion of the optical signals to dedicated optical receivers

37. For optimal optical link performance at different temperatures, where should the input power to a laser fall on the laser's noise power ratio (NPR) curve?

38. Why should you confirm that the hybrid fiber/coax (HFC) portion of the return network is working properly before troubleshooting the transmission level from a cable modem?

39. Which of the following describes the use of the normalized reference sweep trace?

The normalized reference establishes a baseline sweep response that is used to establishthe power level into the return laser.

40. What is a limitation of ingress cancellation?

Ingress cancellation uses proprietary techniques and is only effective with specific cable modems.

Ingress cancellation uses proprietary techniques and Is only effective with specific cable modem termination systems (CMTS).

41. What is the result of filtering when it is applied after modulation?

42. What enables the distribution feedback (DFB) laser to suppress the side wavelengths that limit the use of Fabry-Perot (F-P) lasers and significantly diminish the effects of mode partition noise (MPN)?

DFB lasers use external modulation which enables suppression of wavelengths other than the center wavelength.

DFB lasers distribute and electronically feed back undesired wavelengths to maximum theoutput of the laser but minimize the MPN.

DFB laser have an additional structure that suppresses wavelengths other than the center wavelength.

43. What is a characteristic, of digital modulation using quadrature phase shift keying(QPSK)?

44. Which of the following describes long-loop automatic gain control (AGC)

Long-loop AGC adjusts the receive levels of the customer premises equipment.

Long-loop AGC adjusts the transmit levels from the headend to the customer premises equipment.

Long-loop AGC adjusts the transmit levels of the customers premises equipment.

Long-loop AGC adjusts the receive levels from the headend to the customer premisesequipment.

45. What information can be gathered by a return path monitoring system that captures the quadrature amplitude modulation (QAM) return carrier from a DOCSIS modem?

46. To ensure the best performance, how should the RF output power from the optical receiver be adjusted?

The input to the RF amplifier should be adjusted for the correct RF output from the optical receiver.

47. How can the return path carrier-to-noise ratio (C/n) of a drop system be increased?

48. What information is sent in Data Over Cable Service Interface Specification (DOCSIS) media access control (MAC) data frames to all of the cable modems on the forward carrier to which they are registered?

The transmitted data frames include the transmission frequencies, the modem DOCSISaddress, and the usage intervals for each particular cable modem.

The transmitted data frames include the transmission frequencies, time references, andthe MAC address for each particular cable modem.

The transmitted data frames include collision detection, time references, and the usageintervals for each particular cable modem.

The transmitted data frames include the transmission frequencies, time references, andthe usage intervals for each particular cable modem.