ROC 3 Test Study

What does a PON use to make P2MP connections between the CO and customer premises?

Fiber-to-the-premises topologies.

What fiber-optic cable in a PON typically runs from the CO to the ODN and has a fiber count ranging from 72 to 1,728?

Trunk (feeder) cable

Which optical splitter do FTTH deployments commonly use for large split ratios due to its uniform splitting ratios, low insertion loss, high reliability, and scalability?

Planar lightwave circuit splitter

What role does a fiber-optic splice closure play in a PON?

To provide a sealed, secure environment to join or split fibers without exposure to external elements.

What is the difference between a FAT and a FDH in a PON?

A FAT is a pedestal-mounted enclosure with a lower fiber count than FDH cabinets.

What is an ONU/ONT located outside the customer premises?

A field-hardened device mounted in an environmentally sealed enclosure, often including an internal splice holder for field terminations.

What describes a physical point-to-point (P2P) fiber-optic network topology?

It consists of a dedicated optical fiber connected between network elements without any optical splitters or couplers in the path.

What is the primary disadvantage of using a bus topology in a fiber-optic network?

All devices share the same communication medium, which can lead to data collisions and congestion.

Which describes a feature of mesh topology in network architectures?

It provides three or more redundancy routes for individual nodes, enhancing reliability and flexibility.

In a distributed split network, where is the first level of fiber splitters installed?

In an enclosure near the headend/CO.

What do all hardline splitter, directional coupler, power inserter, and distribution tap housings have on the back?

A threaded mounting tap and strand clamp on the back for attachment to the aerial strand or an underground pedestal.

What can be done when installing hardline splitters, directional couplers, power inserters, and distribution taps in tight quarters, such as in a pedestal?

The seizure screw can be removed, and the hardline connector attached to the side of the housing.

What is on the interior side of the faceplate in a hardline splitter, directional coupler, power inserter, and distribution tap?

The electronic circuitry and male or female faceplate/housing interconnect pins.

In a directional coupler, what is the relationship of the insertion loss between the directional coupler input and through ports, and the amount of signal tapped off from the input?

The more signal tapped off from the input, the greater the insertion loss.

What element in a splitter and directional coupler serves, among other functions, to determine to which ports 60/90 VAC is sent?

Plug-in fuses.

What must be done when measuring the port-to-port isolation between the output ports of a splitter or directional coupler?

Terminate the common input port.

How much does a power inserter impact the RF in a network?

A power inserter should have minimal impact on the RF in both directions.

Which of the following describes a power inserter?

It contains a high-pass filter network that passes RF signals between the two RF/AC ports and blocks the 60-hertz (Hz) AC voltage between the same two ports.

Which characterizes a feed-through distribution tap?

It has a directional coupler that efficiently routes most of the signal to the output port while removing a small amount of the signal and passing it to the splitter network.

Why is it necessary that feed-through distribution taps pass AC?

To pass AC along to power other amplifiers downstream.

Which fiber-optic network design uses optical couplers along a continuous fiber run and is commonly used in rural areas where homes and businesses extend over long distances?

DTA

________ has a breaking strength of up to 20,000 lbs, which allows spans to travel up to 3,000 feet without the support of a strand.

ADSS cable

What option can a passive optical network (PON) operator use to offset some of the initial costs to build their network while also making their network economically viable in the long term?

Leasing spare fibers

Which of these items should be identified on a route map so that the design can provide (or not provide) special network access?

Parks

Which type of map contains fiber count information?

Design map

How many meters of slack cable does a typical aerial installation use?

15 to 25 meters

What is one example of a stipulation in a franchise agreement that would affect network design?

An entirely fiber-optic-based network.

When activating a fiber-optic network, which acceptance-testing stage includes adjusting attenuation levels for the first time?

During equipment activation

What information should always be included in the optical link performance documentation?

Fiber assignments

When troubleshooting an outage in an optical network, why would a technician refer to the sequential markings on a network's as-built documentation?

To help determine specific cable lengths.

How was the bel divided to become a workable unit of measurement?

It was divided into 10 equal units called the dB.

Which of the following best describes a number that compares an amount less than the whole to the whole amount?

A fraction.

How do you convert a fraction to a percent?

Dividing the numerator by the denominator and multiplying by 100.

The starting point of the entire decibel measurement system is the bel, which is clearly defined as a ______ power ratio.

10:1

Which of the following best describes one-tenth bel or 1 dB?

The 10th root of the 1 bel ratio.

What is the input-to-output power ratio of a coaxial cable that has 1 dB of attenuation?

1.2589:1

An input-to-output power ratio of 10:1 has an input-to-output voltage ratio of ______.

3.162:1, the square root of the power ratio.

What is the input-to-output power ratio of 2 bels of a similar impedance cable?

100:1

What is the power ratio for 2 dB?

1.585:1

What is the minimum acceptable signal level of 0 dBmV at TV set inputs?

1 mV across 75 ohms.

Which represents the values expressed in dBmV preceded by a minus sign (-)?

Values of voltage less than 1 millivolt (mV) across 75 ohms.

A signal increase of 1 dB represents a ________ increase in power.

25.89%.

Why do values expressed in dBmV progress nonlinearly compared to a linear mV?

They are based on the logarithms of power ratios.

What is approximately equivalent to a 1 mV decrease in a signal level of 40 dBmV?

A decrease in the level of 0.1 dB.

What are the units that can be used to represent signal level values?

mV, dBmV, and µW or nW.

How much signal is necessary from the subscriber's tap port at 750 MHz to provide a minimum of 3.0 dBmVs to the TV set when the drop is 150 feet of Series 6 cable, and there is just one outlet? (Use 5.65 dBs per 100 feet for the attenuation rate and round off to the nearest tenth of a dBmV.)

11.5 dBmV.

What is the maximum tap value that can be installed when the tap is connected directly to a line extender amplifier output and: (1) the line extender output is 45 dBmV at 745.25 MHz; (2) the longest amount of Series 6 coaxial cable from the tap to either of the two TV sets is 150 feet; (3) the Series 6 coaxial cable attenuation rate is 5.65 dB per 100 feet at 750 MHz; (4) the drop includes a splitter with a 4.0 dB loss; and (5) the system minimum signal level required at each of the two TV sets is 3.0 dBmV?

29 dB.

What happens to a signal when the output of a line extender is 3 dB lower than it normally should be?

The signal is 3 dB lower than normal from that point on.

To maintain a 3 dBmV input signal to two TVs, what would be the minimum signal level at the tap if the drop is 150 feet long with an attenuation rate of 5.65 dB at 750 MHz with a 4-way splitter (-7 dB loss at 750 MHz)?

19 dBmV.

Which of the following best describes load resistance?

Load resistance is the total resistance when the source and wire resistances are very small.

Which of the following best describes current?

Excessive flow for a specific conductor size can cause the conductor to become too hot and melt or burn the conductor's insulating cover.

What is the total DC loop resistance of a 1,850-foot piece of 0.500-inch coaxial cable with a DC loop resistance of 1.34 ohms per 1,000 feet?

2.479 ohms.

How can an installer control the resistance of the drop cable being installed at a customer's premises?

Replace Series 59 with Series 6 cable because the Series 6 cable center conductor is larger in diameter, with lower resistance than Series 59 cable.

Which of the following best describes total resistance in a circuit?

It is the sum of the individual resistances in the circuit.

What happens when the cross-sectional area of a conductor doubles?

Its resistance decreases to half its original value.

What is the total DC loop resistance of a 350-foot piece of Series 59 drop cable when the DC loop resistance of that Series 59 cable is 56.04 ohms per 1,000 feet?

19.614 ohms.

Which term best describes the opposition a material or device offers to the current flow?

Resistance.

How many ohms is the amount of resistance that allows 1 ampere of current to flow when 1 volt of electromotive force is applied to a circuit?

1

What does current flow encounter within a power source when traveling from the positive terminal to the negative terminal?

Source resistance.

Why do digital modulation channels have measurable analog parameters?

It is based on modulating an analog RF carrier with digital data.

Which characterizes a QAM channel?

When of equal amplitude and bandwidth, the power level of a QAM channel is several dB higher than an analog TV channel.

What does the MER measurement of a QAM channel tell a technician?

How close the QAM channel is to the cliff where the number of bit errors exceeds the FEC capacity of the receiver and reception stops.

What type of applications are EVM expressions best suited?

Applications that have small random noise-like errors.

In an adaptive equalizer display, what do the vertical bars to the right of the incident signal, the eighth bar from the right, represent?

How much equalization is being applied to the channel.

When checking the ICFR of a QAM channel in the customer premises, a frequency response with a repetitive ripple is a symptom of what?

Micro-reflections.

Why does the information in STB and modem diagnostic screens often appear cryptic to a customer?

The screens use initials, acronyms, and jargon intended for people that are familiar with the product.

What enables assessment of upstream DOCSIS channel parameters using the QAM analyzer function of a signal level meter (SLM)?

The upstream channels from the built-in DOCSIS modem are optimized for the upstream path and the channel parameters displayed by the instrument.

What does a hole in the center of the QAM constellation symbol error cloud indicate?

Coherent interference from ingress, or a beat from another channel modulator, landing inside the QAM channel.

When a test instrument indicates measurements that fall outside of minimum or maximum requirements, why should a technician recognize what the failed measurements are?

To troubleshoot and resolve the cause of failed measurements.

Which (DOCSIS) layer is used by (CMTS) to differentiate between cable modems?

The DOCSIS (MAC) Layer.

What was introduced in DOCSIS 3.0 to allow enough bandwidth for upstream carriers from previous DOCSIS versions?

The option to increase the top frequency of the upstream to 85MHz.

In a DOCSIS network, why is the data throughput over the return or upstream path typically less than the throughput of data over the forward or downstream path?

Compared to the downstream path, the narrower bandwidths and lower orders of modulation used to transport data over the return path cause the downstream and upstream data throughput to be unequal or asymmetrical.

What would be the downstream throughput if two QAM channels with a throughput of 38 Mbps were bonded?

76 Mbps.

What are two features that were added in DOCSIS 3.1 to extend the viability of HFC networks into the next decade?

(OFDM) and (LDPC).

How does IP multicast differ from IP broadcast?

IP multicast traffic is only sent to specific modem addresses on the network; IP broadcast traffic is sent to all modems on the network.

When using a digital signal analyzer to troubleshoot data throughput in the DOCSIS network, what is the minimum MER into the cable modem for a 256-QAM carrier?

32 dB or greater.

What layers of the OSI reference model are specific to cable networks and are present only between DOCSIS modems and the CMTS?

Layers 1 through 4 (Physical layer, Data Link Layer, Network Layer, and Transport Layer) are applied between the DOCSIS modem and CMTS.