Brainscape Deck Flashcards
The topology where signals originate in the headend andare 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 1953for 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 andbranch architecture are:
BandwidthImpairmentsDependency on Power
The lowest possible power level determined by the thermal noise generated within the electrical componentsbeing 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 mixingof 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 QualityIncreased ReliabilityDecreased cost of system maintenanceCost effective system bandwidth upgradesCost means of system upgrade requiring a complete change our of electronicsSmall 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 CATVindustry
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 centerwavelength to be carried on a single optical fiber.
Dense Wave Division Multiplexing (DWDM)
Three parts of the optical link
Fiber Optic CableTransmitter (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 pulsesof 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 CascadesFewer/smaller outages due to segmenting the system into smaller areasImproved picture Quality
FTTF
Fiber to the Feeder
Advantages of FTTF
Shorter CascadesFewer/smaller outages due to segmenting the system intosmaller 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 nodeNo CascadeFewer/smaller outages due to segmenting the system intovery small areasIncreased Bandwidth
A fiber-based network which uses passive splitters todeliver signals to multiple locations
Passive Optical Network (PON)
FTTH
Fiber to the Home
6 advantages of FTTH
Passive networkSingle fiber is dedicated to each subscriberFeatures local battery backup, no large remote power supplies are required.No exterior active devicesNo CascadesIncreased 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 thenetwork.
Redundancy
Comcast’s goal for network reliability
“four-nines” or 99.99%
A network architecture where nodes, hubs, or headendsmay be connected with fiber optic cables to provideredundancy 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
SamplingQuantizationEncoding
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 withina 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