NCT5 Flashcards
The topology where signals originate in the headend and
are transmitted long distances via trunk cables
Tree and Branch
A network architecture that typically uses fiber optic cables to bring signals to selected areas of the system called nodes
Hybrid Fiber-Coax (HFC)
Bi-annual tests, performed in the headend and at a number of end-of-line location
FCC Proof-of-Performance
The cumulative effect of return path distortions they are added to the signal at various locations in the coaxial portion of the network.
Funnel Effect
Specifications standards approved by the FCC in 1953
for commercial analog color TV broadcasting.
National Television Standards Committee (NTSC)
a portion of the electromagnetic spectrum whose frequencies are well suited for transmitting and receiving Telecommunications signals through the air.
Radio Frequency (RF) Spectrum
Signals that flow downstream, from the headend to the network.
Forwards (Downstream) Signals
Signals that flow in the upstream direction, from customer to headend
Revers (upstream) Signals
Device that separates or combines based on frequency.
Diplex Filter
typical cutoff frequency for a sub-split diplex filter
About 50 MHz
The three major concerns/ limitations of the tree and
branch architecture are:
Bandwidth
Impairments
Dependency on Power
The lowest possible power level determined by the thermal noise generated within the electrical components
being tested
Noise Floor
The highest power level (amplitude) reached by a carrier
Peak
A clustering of beats 1.25 MHz above the visual carriers in a CATV network
Composite Second Order (CSO)
A form of interference or noise resulting from the mixing
of all of the various carriers in a CATV network
Composite Triple Beat (CTB)
Two major types of distortions that are typically associated with CATV
Composite Second Order (CSO) and Composite Triple Beat (CTB)
The 6 benefits of implementing fiber optics in broadband networks
Enhances Picture Quality
Increased Reliability
Decreased cost of system maintenance
Cost effective system bandwidth upgrades
Cost means of system upgrade requiring a complete change our of electronics
Small segmented areas allow greater return path functionality
Having or relating to a frequency below the audibility range of the human ear.
Infrasonic
A stream of atomic nuclei that enter the earth’s atmosphere from outer space at speeds approaching that of light
Cosmic Rays
Frequency range of satellite systems
4GHz to 13GHz
The wavelengths most commonly used by the CATV
industry
1310nm and 1550nm
The type of fiber optic cable that the broadband industry uses
Single Mode Fiber
The process of combining multiple carriers onto a single medium
Multiplexing
Width of the Fiber optic core
8-10um
Width of the fiber optic cladding
125um
Width of the fiber optic coating
250um
Combines multiple optical signals in order to amplify them as a group and transported over a single fiber
Wave Division Multiplexing (WDM)
Allows multiple wavelengths above and below a center
wavelength to be carried on a single optical fiber.
Dense Wave Division Multiplexing (DWDM)
Three parts of the optical link
Fiber Optic Cable
Transmitter (Laser)
Receiver (Node)
Individual fibers are bundled and then placed into these to reduce the possibility of damage
Buffer Tubes
This diode changes the RF signals to pulses
of light and then transmits them onto an optical fiber
Semiconductor Laser Diode
The Three types of optical transmitters that are typically used in broadband HFC Network
Fabry-Perot (F-P)
Distributed Feedback (DFB)
Yttrium-Aluminum-Garnet (YAG)
YAG
Yttrium-Aluminum-Garnet
DFB
Distributed Feedback
F-P
Fabry-Perot
A spare fiber installed during the construction of the network that was reserved for future use.
Dark Fiber
Three advantages of trunk reduction
Shorter Cascades
Fewer/smaller outages due to segmenting the system into smaller areas
Improved picture Quality
FTTF
Fiber to the Feeder
Advantages of FTTF
Shorter Cascades
Fewer/smaller outages due to segmenting the system into
smaller areas.
Increased Bandwidth
FTTC
Fiber to the Curb
PON
Passive Optical Network
Consists of a transmitter at the Headend and a receiver near the subscriber. Requires a power supply near the node but all other actives have been removed
FTTC PON
4 advantages of FTTC
No active devices after node No Cascade Fewer/smaller outages due to segmenting the system into very small areas Increased Bandwidth
A fiber-based network which uses passive splitters to
deliver signals to multiple locations
Passive Optical Network (PON)
FTTH
Fiber to the Home
6 advantages of FTTH
Passive network
Single fiber is dedicated to each subscriber
Features local battery backup, no large remote power supplies are required.
No exterior active devices
No Cascades
Increased Bandwidth
This will ALWAYS be considered the “Backbone” in an HFC Network
The Fiber Network
A high-speed line or series of connections that forms a major pathway within a network
Backbone
The duplication of certain pieces and/or portions of the
network.
Redundancy
Comcast’s goal for network reliability
“four-nines” or 99.99%
A network architecture where nodes, hubs, or headends
may be connected with fiber optic cables to provide
redundancy or increase services
Ring Architecture
Builds upon ring technology by adding a second (redundant) ring connecting the nodes to the headend. The second ring typically takes a different path
Ring within a Ring
A facility between the headend and the customer that performs many of the functions of a headend
Hubsite
Similar in function to a hubsite, but serving fewer customers
Optical Transition Node (OTN)
Usually a passive device such as a splitter or directional coupler used to combine radio frequency signals from one source with those from another
RF Combiner
Usually a passive device that divides a signal into two equal paths. It may be found on trunk, feeder, or drop cable.
RF Splitter
Device used to combine the channels for entry onto the cable or fiber optic transmitter
Headend Combiner
The difference, in dB, of a signal level, injected into one output port, and the measured level of that same signal on another output port, with the input port properly terminated.
Port-to-port isolation
Obtained by measuring the attenuation between the two output ports (A and B) when the common port (input port) is terminated in the correct value of impedance. An RF generator signal is applied to port A and an RF voltmeter reading is taken at Port B.
Isolation
Provision for connection to a device such as a tap, splitter, set-top box or computer
Port
Used to combine all of the signals to be carried over the cable system into a single medium (cable) for routing to the laser transmitters that are feeding the optical nodes in the system
Headend Combining Network
A measurement of the reflected signal compared to that of the incident signal
Return Loss
Device used to divide or combine light carriers on fiber optic cables.
Optical Splitter
A discontinuous signal whose various states are discrete intervals apart.
Digital Signal
Device used to convert an analog signal to a digital signal.
Digitizer
takes an amplitude measurement of the waveform at fixed intervals of time, and converts them to a binary number
Digitizer
The smallest unit of computerized data. Bits are defined as single characters of 0 or 1. Bandwidth is usually measured in bits-persecond.
Binary Digit (Bit)
A set of Bits that represent a single character. Usually there are 8 Bits in a Byte, sometimes more, depending on how the measurement is being made.
Byte
The number of changed states that can occur per second.
Baud
The value of “On” in a binary system
“1”
The value of “Off” in a Binary system
“0”
How many bits are in a “Nibble”?
4
In ASCII #5 alphabet, how man bits are in a byte?
7
If start and stop bits are included with Asynchronous Communications, then how many bits are in a byte?
10
ADC
Analog to Digital Conversion
DAC
Digital to Analog Conversion
A continuously varying signal with an unlimited number of possible values of amplitude and frequency.
Analog Signal
a non-continuous signal or carrier that changes its output in discreetly timed steps of voltage level and/or phase that can represent numerical values or other information
Digital Transmission
3 steps of basic ADC
Sampling
Quantization
Encoding
The “Measuring” of the analog signal at specific intervals.
Sampling
The assigning of a specific value to each of the samples
Quantization
The process by which Quantized values are converted into a data or bit stream
Encoding
ASK
Amplitude Shift Keying
FSK
Frequency Shift Keying
QPSK
Quadrature Phase Shift Keying
QAM
Quadrature Amplitude Modulation
The process of varying the amplitude, frequency, or phase of a carrier to be in step with the instantaneous value of the modulating waveform
Modulation
Data transmission scheme wherein the carrier is shifted in amplitude
Amplitude Shift Keying (ASK)
The carrier frequency is shifted to represent the difference between a one and a zero
Frequency Shift Keying (FSK)
The position on a waveform cycle at a specific point in time. One cycle is defined as 360 degrees of this
Phase
Digital modulation scheme wherein the carrier is shifted in 90 degree steps. There are four possible phase states and the magnitude is constant.
Quadrature Phase Shift Keying (QPSK)
BPSK
BiPhase Shift Keying
In QPSK, what does “I” stand for?
In-Phase
In QPSK, what does “Q” Stand for?
Quadrature - shifted 90* or one quarter of a cycle
A graphic depiction of the four phase states of a Quadrature Phase Shift Key signal.
Constellation Diagram
What is the bandwidth of QPSK in a 6MHz bandwidth?
10 Mb/s
Digital modulation scheme that changes the phase and the amplitude.
Quadrature Amplitude Modulation (QAM)
a digital transmission technology that splits the frequency band into a number of channels. The channels are each assigned a specific time slot, so that several transmissions can share a single channel without interfering with one another
Time Division Multiple Access (TDMA)
The digital equivalent to Signal-to-Noise
Modulation Error Ratio (MER)
A joined or connected group of devices
Network
A network of computers linked by cable within a building or office complex.
Local Area Network (LAN)
A network of multiple locations linked by cable within
a city or campus
Metropolitan Area Network (MAN)
A network typically bigger than a city or metropolitan area.
Wide Area Network (WAN)
A data network connects each of its endpoints to the network with a single link. A central device (hub) is used to aggregate and distribute data traffic to all endpoints and/or other central points in what’s referred to as a clustered star.
Star
Consists of several star networks that have been linked together
Clustered Star
Topology where workstations are connected to the network through a common path
Bus
A topology in which a data frame is passed around. As it arrives at an endpoint, the endpoint can either pass it along to the next endpoint or attach information to be sent to a destination
Token Ring
A network architecture where nodes, hubs, or headends may be connected with fiber optic cables to provide redundancy or increase services.
Ring
A method of data transmission that allows characters to be sent at irregular intervals by preceding each character with a 0 and by ending each character with a 1. This is referred to as start (0) and stop bits (1). It is the method, which most PCs use to communicate with each other and mainframes
Asynchronous Transmission
An extra bit added to help check if the data that is
being transferred is correct
Parity Bit
The condition that occurs when two events happen in a specific time relationship with each other and both are under control of a master clock. Characters are spaced by time, not by start and stop bits.
Synchronous Transmission
Synchronizing bits used in synchronous transmission to maintain synchronization between transmitter and receiver.
Sync Bits
SNMP
Simple Network Management Protocol (SNMP)
NE
Network Elements
MIB
Management Information Base
A unique number assigned to a piece of equipment
used for identification purposes.
Media Access Control Address (MAC)
UTP
Unshielded Twisted Pair
signaling rate of 10BaseT
10 Mb/s
Signaling rate of 100BaseT
100 Mb/s
The designation for Ethernet over fiber optic cable, primarily for point-topoint links
10Base-F
Ethernet resides in what layers of the OSI model?
The 2 lowest levels (layers)
This device works as a multiport signal repeater, broadcasting an incoming signal to all other ports on an ethernet network
Ethernet Hub
The four-part numeric address that is assigned to a computer or an account as an identification tool
Internet Protocol Address (IP)
IEEE MAC Protocol for Hybrid Fiber-Coax Networks; standard for data communicatons over a cable network
802.14
The Four original partners of MCNS (Multimedia Cable Network Partners Ltd.)
Comcast, Cox, TCI and Time Warner
The three companies that joined MCNS in late 1996
Media One, Rogers Cablevision and CableLabs
DOCSIS
Data Over Cable Service Interface Specification
When was DOCSIS 1.0 released? (Month and Year)
March 1997
The Leading standard for cable modems
DOCSIS
Four devices that must be added to a system to offer high-speed internet
CMTS (Cable Modem Termination System)
CM (Cable Modem)
Servers
Noise Filters
A unit consisting of various hardware and software entities that acts as the hand-off point between the RF based HFC network and other networks such as the
Internet and the PSTN.
CMTS (Cable Modem Termination System)
Used to terminate, manage and translate high-speed Internet sessions between cable modems in a LAN and other devices in a WAN.
CMTS (Cable Modem Termination System)
The collection of computers accessed through the Internet. Uses a hypertext based system for finding and
accessing its resources.
WWW (World Wide Web)
Four Items that a CMTS manages
Time Slots
Contention Slots
Modem Data
Transmit Levels
Each cable modem is assigned one of these by the CMTS and only one modem is allowed to transmit during this.
Time Slot
These slots are usually used for short data transmissions such as a request for an additional number of reserved time slots
Contention Slots
The signal level that the CMTS wants to “See”
0dBmV
A PC on a LAN from which information or applications are requested.
Client/Server
A computer circuit board (card) installed in a computer so that the computer can be connected to a network. Provide a dedicated, full-time connection to a network.
NIC (Network Interface Card)
Why is it called a cable “Modem”?
When they transmit data they “MOdulate” the data onto a carrier, then receive data and “DEModulate” it from the carrier and send it on to the computer
Four of the most common servers found in a braodband network
DHCP
TOD
TFTP
Proxy
This server sets up the MAC and IP addresses for the cable modem.
DHCP Server
Dynamic Host Configuration Protocol
This server sets up a common clock between the CM and the CMTS
TOD Server
Time of Day
This server allows non-protected file transfers, such as a
configuration file for a modem.
TFTP Server
Trivial File Transfer Protocol
These servers store commonly used (or contractually stored) data. A network may have a series of these servers located in different places.
Proxy Server
The two types of noise filters
High Pass Filter
Notch Filter
These types of filters only allow signals above 50MHz to pass through the filter
High Pass Filter
In addition to letting everything above 50 MHz to pass, this filter allows a small spectrum below 50 MHz to pass
Notch Filter
The process of setting up the connection between the
CMTS and the cable modem, where transmit levels and
frequency are determined.
Ranged
A switch or collection of switches connecting multiple networks
POP (Point of Presence)
The point of access into the
Internet.
NAP
Network Access Point
The company who provides access to the Internet and the World Wide Web, who usually also provides core
features such as e-mail.
ISP
Internet Service Provider
The local, long-distance and international
phone system in use today
PSTN
Public Switched Telephone Network
This device in the Headend controls the operation of CDV.
HDT
Host Digital Terminal
Three major components of the Host Digital Terminal
Access Bandwidth Manager Shelf
Modem Shelf
Spectrum Manager Shelf
This Shelf provides the connection between the Network Interface Unit (NIU) and the switch, or more simply, the connection between the HDT and the LEC
ABM
Access Bandwidth Manager
The point of demarcation between the network and the customer. It contains the modem necessary for telephony over a cable network.
NIU
Network Interface Device
The device that opens or breaks the circuit path in a telephone call. This device looks at the incoming data to determine where the data should get routed.
Switch
The local phone company is also known as what?
LEC
(Local Exchange Carrier
Shelf on the HDT (Host Digital Terminal) that converts the digital telephone signals into digital signals that are then modulated onto an RF carrier to be transmitted over the HFC Network.
Modem Shelf
This shelf on the HDT (Host Digital Terminal) monitors the RF spectrum allocated for telephone services over the HFC network. If problems are detected, it can switch the data transmission (telephone call) to another frequency.
Spectrum Manager
How many subscriber telephone lines can an NIU Handle?
4
LPSU
Local Power Supply Unit
The process of setting up the connection between the HDT and the NIU, where transmit levels and frequency are determined.
Marshalled
Modulating technique that interweaves multiple conversations, based on time.
TDMA
Time Division Multiple Access
The number of the person that you
are trying to call.
Terminating Number
The phone company of the person you are trying to call.
Terminating LEC
The “local” phone office where the subscriber’s lines are connected to the switching equipment.
Central Office
What is “7” equal to in binary?
0111
64 QAM has how many phase angles?
52
16 QAM has how many phase angles?
10
The distance between two points of like phase
in a wave.
Wavelength
A card made up of material similar to photographic film that changes colors when exposed to light.
Photosensitive Card
ANSI Laser standard that separates lasers into various classes that take into consideration the operating wavelength, output power level and whether the laser operates as a continuous or pulsed light output
Z-136
Four nines works out to how many minutes of down time per month?
4.5 minutes
loss of service to our
customers due to a fault in the
delivery network.
Outage
Minimum telephone service to assure a contact in case of an emergency.
Lifeline
FCC Standards CFR 47, Part 76.605(a)(1-12)
Proof-of-performance (POP) test
A continuous wave (CW) frequency onto which information is modulated for transport.
Carrier Frequency
Maximum Bandwidth of 256QAM
42.88Mbps
How long must POP tests be kept at the local office?
minimum of 5 years
how many test points are required for 1,000 to 12,500 customers?
6
How many test points are required for each additional 12,500 customers?
1
Channel requirements for POP testing (amount)
4 channels plus one additional channel for every 100 MHz.
In a cable system with an upper frequency at 750 MHz, how many test channels must be used?
11 Channels
All channels must be tested during these 3 tests.
Video Carrier Level, Audio Carrier Level, Video Carrier Level Stability Test
Only one Channel needs to be tested during this non-frequency specific test
Hum Modulation
How many digital channels must be tested on an all digital system with an upper frequency of 862MHz?
0, digital channels are not included and are not tested.
The amount of channels during these tests are based solely on the highest operating frequency
Video-Audio Carrier Frequency Separation
In-Channel Response
Carrier to Noise
Coherent Disturbances Tests
This test must be performed twice a year, once during the coldest months and again during the warmest (Jan-Feb and Jul-Aug respectively)
Video Carrier Level Stability (24-hour) test
This POP test must be performed every three years
Color Performance test
A circuit that automatically adjusts the gain of an amplifier so that the output signal levels stay constant despite varying input levels.
Automatic Gain Control (AGC)
a spectrum analyzer feature that allows the user to make otherwise intrusive FCC POP tests in a non-intrusive manner.
Gated Testing
When planning POP tests, these four things need to be considered
Test times
Channels and programming affected by testing
Test lengths
Ability to perform non-intrusive gated testing
This test is usually performed by a Headend tech rather than a System Tech
Color Performance
What would a Discrepancy statement include?
Explain all possible misinterpreted fails, such as test point relocation, added channels, encoding issues and so on.
POP measurements are to be taken at what location?
Input to the subscriber terminal
EIA
Electronic Industry Association
What must an operator do in order to pass the receivability test?
Submit documentation showing that their channel lineup conforms to the EIA Channel allocation plan
What does the Audio Carrier Frequency Test ensure
That the audio carrier frequency for each channel must be 4.5MHz above the video carrier frequency, +/- 5kHz
Where is the Audio Carrier Frequency test performed at?
The Headend as well as the field test points
How many times a year is the Audio Carrier Frequency test performed?
Twice annually
What type of set-top box can alter the Audio Carrier Frequency?
Baseband set-top boxes (as opposed to non-baseband)
What six measurements are taken during the 24-hour test?
Minimum Visual Signal Level Visual Signal change Adjacent Visual Signal Any Other Visual Signal in Bandwidth Visual Carrier Level Audio Carrier Level
The six measurements that are taken during the 24-hour test are performed on what channels?
All NTSC Channels at each test point location
What is the Minimum Visual Signal Level allowed at the end of a 30-meter (100’) cable drop that is connected to the subscriber tap?
1.41mV across an internal impedance of 75 ohms (+3dBmV
CT 5-3-22
The square root of the sum of the squares of the amplitudes of individual components of a function, such as the frequency components of a signal.
Root Mean Square (RMS)
Maximum variation of each channel within any six-month period at the end of a 30-meter drop cable
8dB
Adjacent Visual Signal deviation of the visual signal level of any visual carrier within a 6MHz nominal frequency separation
3dB
What is the maximum “spread” or deviation among ALL channel levels in a 300MHz cable system and what is the incremental increase
10dB
1db per 100MHz
At what level must the aural signal be maintained in association with the visual signal level?
between 10dB and 17dB below the visual signal level
At what level must the aural signal be maintained in association with the visual signal level on a baseband converter.
between 6.5dB and 17dB below the visual signal level.
In a 24-hour test, how many times must the signal level be checked?
four times
What are the time intervals of the 24-hour test?
5 to 7 hours
at what frequency is the In-Channel Response test performed?
.75MHz to 5Mhz above the lower frequency boundary of the cable channel under test
What is the FCC In-Channel Response requirement?
+/-2dB or 4dB peak-to-valley
To perform this test, a signal must be inserted on the channel, either by the headend technician or by other means
In-Channel Response Test
FCC Requirement for C/N
43dB at each test point
What are the three type of coherent disturbances?
Composite Second Order (CSO)
Composite Triple Beat (CTB)
Other interfering signals (i.e. Ingress)
What is the FCC requirement for Coherent Disturbances?
51dB below the desired carrier level for STD plans and 47dB in IRC and HRC systems
The goal of this test is to find the worst beat or interfering signal, regardless of it’s type
Coherent Disturbances Test
FCC requirement for isolation
18dB
Because the FCC allows you to submit manufacturers specifications to prove compliance, you rarely need to perform this test:
Terminal Isolation Test
FCC requirement for Hum Modulation
less that 3% of the video carrier level.
Where is the Hum Modulation test done?
the end of a 30m or 100’ drop
how many channels is the Hum Modulation test performed on?
One channel per test point
How many channels is the Coherent Disturbance test performed on?
Dependent on highest frequency
What are the three Color Performance tests?
Chrominance to Luminance Delay Inequality
Differential Gain
Differential Phase
FCC Spec for Chrominance to Luminance Delay test
Within 170 nanoseconds
FCC Spec for Differential Gain
Within +/-20%
FCC Spec for Differential Phase
Within +/-10 degrees
Who usually performs the color performance tests?
The Headend Technician
How many channels are recommended to be tested during the Color Performance test?
All NTSC or similar channels
How often are the Color Performance Test performed?
once every three years
Allowable signal leakage level below 54MHz
Up to 15uV/m @ 30m
Allowable signal leakage level between 54MHz and 216 MHz
up to 20uV/m @ 3m
Allowable signal leakage above 216MHz
up to 15uV/m @30m
The two types of leakage monitoring frequency.
Continuous Monitoring
Quarterly Monitoring
Two types of annual leakage monitoring methods
Ground Based
Flyover
What is the minimum cable strand sample allowed during a ground based leakage measurement?
75%
What leaks are included in the CLI calculation?
All leaks 50uV or greater
what is the elevation that a flyover is completed at? (in meters)
450m
1476’
Two requirements for monitoring of plant with a handheld signal leakage detector
- Must be properly calibrated to detect a leak of 20uV/m or greater @ 3m
- Perform all measurements with a horizontally polarized dipole antenna, preferably located no more than 3m from the leak and 3m from the ground
What does a Spectrum Analyzer Display?
information in the amplitude (vertical) vs. frequency (horizontal) domain over the entire spectrum or portions of it.
comparable in certain respects, typically in a way that makes clearer the nature of the things compared.
Analogous
This filter has a bell-curved “shape,” which it applies to all energy passing through it.
Resolution Bandwidth Filter (RBW)
This is a low-pass filter at the analyzer detector’s output. This filter takes the RF energy associated with the video modulation on the carrier that has already passed through the RBW filter and the detector and smoothes it out
Video Bandwidth Filter (VBW)
CT 5-3-39
The signal to an analyzer is injected here
RF Input
Used when accessing analyzer’s gated mode, such as in the C/N POP test
TV Input Connector
The main setting and adjustment keys for the analyzer functions and the display. These keys are most often used in the analyzer’s manual testing modes
Function Keys
Additional keys whose action changes depending on the selected analyzer mode or function. Most often used in the analyzer’s automated testing modes
Softkeys
The principal keys useed in the analyzer’s manual modes of operation. They represent the three most basic functions of any spectrum analyzer
Frequency, Span and Amplitude keys
Adjusts the value or amount for the selected function or measurement
Adjustment Knob
Adjust value or amount in incremental steps for the selected function or measurement
Step Key
Allows direct input of a specific value or amount for the selected function or measurement
Numeric Keypad
Sets the type of measurement unit, such as kHz or MHz, for the selected function or measurement
Measurement units’ keys
Marker function and trace control keys
Access marker functions and set trace control functions such as display line, RBW and VBW
Sets analyzer modes, presets and stores or recalls analyzer trace
Mode select Key
Maximum input power of HP 8591C
+72dBmV
Maximum input power of Tektronix 2715
+69dBmV
This must be used when high input levels are required to the analyzer to avoid input overload
preselector
For the greatest accuracy, how should the carrier peak be adjusted?
To the analyzer’s reference level (top of the display)
Three tests that can use gated mode on the HP 8591C
Carrier to Noise
Coherent Disturbances (CSO measurement only)
In-Channel Response
states that in order to obtain an accurate recreation of a signal, it must be sampled at a rate of at least twice the highest frequency
Nyquist’s Rule
What is the minimum and maximum signal level of a 256 QAM channel?
-8dBmV to +10dBmV
What is the minimum MER of a 256 QAM channel?
33dB
What is the minimum Pre BER of a 256 QAM Channel?
less than 1.0E-07
What is the minimum Post BER of a 256 QAM Channel?
less than 1.0E-09
What is the maximum DOCSIS TX level?
Less than or equal to 53dBmV
In a constellation diagram, this is when the outer dots are pulled to the center while the ones nearer the center are unaffected
Compression
In a Constellation Diagram, this is where the dots appear as an arc as you look toward the outer edge of the display
Phase Noise
In a Constellation diagram, this will cause the dots in the clusters to appear to form circles
Coherent interference
In this distortion, the distance between the clusters on the I axis are greater, or lesser, than that of the Q axis
I Q imbalance
Coherent interference can be caused by one of four things, these are:
CTB, CSO, Beats and Ingress
Improperly installed connectors and jumpers, contamination of the connector, improper cable routing or a localized failure fall under this optical failure category:
Patch Panel Related
Over or under-driving the optical transmitter falls under this optical failure category
System Related
Due to causes such as improper bending radius or a clamped cable falls under this optical failure category
Installation Related
Normally due to construction and work related activities, it can also be damaged by improper installation techniques, gunshots, falling branches and automobile crashes. These types of failure incidents fall under this fiber optic failure category:
Construction Related
Good isolation in the headend reduces…
Adjacent Channel Interference
Continuously varying signals
Analog Signals
A mathematical representation of an analog signal
Digital Signal
Why can signals travel great distances w/ little to no noise and distortion degrading the signal
Signals are regenerated rather than amplified
the 2 most commonly used digital modulation schemes that use a combination of changes
QPSK and QAM
QPSK has ____ Phase states
4
A combination of QPSK and ASK
QAM
Device used to analyze digital signals
QAM Analyzer
Graphic depiction of digital signals
Constellation
Ratio of the error power to the average power in the ideal QAM signal
MER
Bits are added to the digital signal in order to detect errors
FEC
Errored bits compared to total bits
BER
The position on a waveform cycle at a specific point in time
Phase
Digital power measurement is _______ power
Average
Analog power measurement is ____________ power
Peak
Peak power of a carrier is known as
Amplitude
Standard for cable modems
DOCSIS
Terminates, manages, translates HSI between the Cable Modems on the HFC LAN and other devices on the WAN
CMTS
Decodes ethernet signaling info for incoming packets and applies filtering rules
Router (Ethernet Router)
Difference between the incident signal and the reflected signal is called:
Return Loss
This laser is good for many channels, has low noise and is good for long distances
DFB (Distributed Feedback)
Laser that is noisy and only good for a few channels and short distances
F-P (Fabry Perot)
Light travels in the core of the fiber because of this concept:
Total Internal Reflection
The ratio of the velocity of light of 2 mediums is called
Index of Refraction
Light reflected in the core is called
Total Internal Reflection
Light travels faster in the ______ because it has a ______ Refractive index than the ________
1) Cladding
2) Lower
3) Core
How is light amplified in a LASER?
Stimulated Emission of Radiation
Which ANSI Class laser is a hazard if the direct or reflected beam is viewed?
Class 3B
ANSI Class laser hazard if the beam is collected on the eye
Class 3A
Example of a Class 3A laser
Laser Pointer
ANSI class laser hazard if beam is viewed
Class 2/2A
Example of a Class 2/2A laser:
Barcode Scanner
All of the losses between Optical Transmitter and Receiver:
Loss Budget
1mW = _____dBm
0dBm
10mW = ____dBm
10dBm
A doubling/halving of the optical power (mW) is equal to a ______dBm change
3dBm
Splice loss is measured using a ______
OTDR
Equation to convert mW to dBm
10Log(mW)
Equation to convert dBm to mW
10^(dBm/10)
Fiber is in tubes much larger than the fiber allowing the fiber to move freely in this cable configuration
Loose Tube
Similar to loose tube but has 2 steel strength members in the jacket
Flex Tube
A method of attaching 2 fiber ends w/ a plastic form to align the fiber ends
Mechanical splice
Clean fiber with this liquid:
at least 90% Isopropyl alcohol
A temporary splice that uses and index matching gel
Mechanical splice
Removes the coating from the fiber
Fiber Stripper
Scores then breaks the fiber
Cleaver
Uses an electrical arc to join two fibers
Fusion splicer
Comcast spec for splice loss
.05dB
Uses a computer program and a video magnifying system to align the fiber ends for splicing
Profile alignment
Uses a transmitter and a receiver to determine if the fiber ends are aligned before splicing
LID (Local Injection and Detection)
A string used to separate and cut the outer jacket and armor
Rip Cord
Splice kits should be bonded to the strand using a _______ and a _________
6 ground wire and a strand clamp
According to the NCT5 book, name three places to store fiber paperwork
1) Splice Trailer
2) Restoration Kit
3) Headend
This is described as the widening of light pulses
Dispersion
This fiber connector offers a good balance between loss and reflections
SC
This fiber connector is the most commonly used
SC
This fiber connector provides a notch and screw connection
FC
This fiber connector end has a flat cut… Reflections travel straight back to the source
UPC
This connector end directs reflections into the cladding
APC
What is used to clean fiber connectors?
Dry wipe cleaning tape dispenser
What is used to clean fiber receptacles?
Lint free wand/swab
interface between the headend and the RF plant
Node
How many nm apart are the DWDM wavelengths? How many GHz is this?
.8nm
100GHz
What is the optimum optical input to a node in dBm and mW?
0dBm
1mW
This part of the optical receiver detects light and converts it to RF
Photodiode
List the two optical amplifiers
EDFA
YEDFA
Having an alternate feed for backup is called
Redundancy
This is used to visually see losses, breaks and distance measurements in the fiber link
OTDR
The ______ uses backscatter to make measurements
OTDR
Main source of loss in fiber
Scattering (Rayleigh)
The downward slope of the OTDR trace shows
Attenuation
Connectors will have both ________ and _______ on the OTDR trace
Reflection and Loss (or attenuation)
The distance the OTDR can’t see is the _______ ______
Dead Zone
To overcome the dead zone, you should use a ________ _______ to make up for it
Launch Jumper
Device that measures light power
Optical Power Meter
Measures light loss
OTDR
This is typically considered an upgrade where some trunk cables have been replaced by fiber and bandwidth is not increased
Trunk Reduction
This is where the entire trunk is replaced with fiber, the entire distribution in replaced w/ new cable and electronics. This is considered a rebuild
FTTF (Fiber to the Feeder)
All actives are removed except for the node. there are no cascades and only taps after the node
FTTC (Fiber to the Curb PON)
This is a PON with no active components between the headend and subscriber with a single fiber dedicated to each sub
FTTH (Fiber to the Home)
also known as out current FTTP (Fiber to the Premise)
Device that measures pulling tension applied to the cables
Dynamometer
Device that prevents excessive pulling tension applied to cables
Breakaway swivel
Clearance at the pole between cable and power
40”
Device used to prevent strand sag when installing strand
Strand Brake
Scanning down the road 12-15 seconds equals what distance range for city driving?
1 to 1-1/2 blocks
Scanning down the road 12-15 seconds equals what distance range for Highway driving?
1/4 to 1/2 mile
The 3-4 second rule is used to determine
Following distance
Before climbing a ladder that is 20’ tall, how far should it be pulled from the base
5’
Max vehicle slope to go up in an aerial lift
5*
Safe approach distance to wires containing up to 300VAC
No contact
Resistance of a circuit to AC
Impedance
Pulling technique used for very long cable pulls through ducts
Mid Pull
CRAN
Converged Regional Area Network
Variation in delay, arriving sometimes in the same order but different time spacing between packets
Jitter
Delay in time of arrival of packets
Latency
QOS
Quality of Service
DQOS
Dynamic Quality of Service
CBONE
Comcast Backbone - Connects regions or CRANs
Mathematical representation of an Analog Signal
Digital Signal
A continuously varying signal
Analog Signal
Optical power units (two)
mW
dBm
RF Power Units (two)
dBmV
mV
Good Isolation in the headend combining reduces:
Adjacent Channel Interference
In NCT5 book, how man dB is good isolation?
25dB
This fiber topology reduces amp cascades and improves picture quality
Trunk Reduction
Cost effective way to get many optical signals transported
WDM
an OTDR uses this to make measurements
Backscattered light
If you want to OTDR great distances, you must increase the _________ _________ to see farther down the fiber
Pulse Width
The difference between the incident signal and the reflected signal
Return loss
Directs frequencies of one bandwidth to one port and frequencies of another bandwidth to another port
Diplex Filter
What is the angle of an APC connector?
8-12 degrees
