TDMM Chapter 11 Flashcards
ACR-F
Attenuation to Crosstalk Ratio - Far End
Performance parameter based on a crosstalk measured on a disturbed pair at the opposite end from which the disturbing signal is transmitted and normalized by the attenuation loss of the disturbed wire pair
ACR-N
Attenuation to Crosstalk Ratio - Near End
The ratio between the signal strength arriving at the end of a link and the disturbance casued by the NEXT coupling from a disturbing wire pair
Attenuation
Decrease in magnitude of power of a transmitted signal between two points
Expresses the loss of optical fiber cabling
CP
Consolidation Point
Interconnection for cables for horizontal cabling to furniture pathways
Delay Skew
Difference in propagation delay between fastest and slowest pairs in same cable sheath
EMI
Electromagnetic Interference
Energy that has an undesirable effect on signal or transmission
Fresnel Reflection
Whenever light travelling in material encounters a different density material, some is reflected back to source
Insertion Loss
Loss in signal from insertion of a component, link or channel
Insertion Loss Deviation
Difference between expected and actual insertion loss
MUTOA
Multi User Teelcom Outlet Assembly
A grouping in one location of serveral telecom outlets
NEXT
Near End Crosstalk
A measure of the signal coupling between any two pairs along the entire length of a balanced twisted pair cable
NVP
Nominal Velocity of Propagation
Determines speed of transmission along a cable relative to speed of light
OTDR
Optical Time Domain Reflectometer
Tool that measures transmission characteristics of opetical fiber
PSAACRF
Power Sum Attenuation to Alien Crosstalk Ratio at Far End
A ratio in decibels that subtracts attenuation from PSAFEXT betweeen close cables
PSAACRN
Power Sum Attenuation to Alien Crosstalk Ratio at Near End
A ratio in decibels that subtracts attenuation from PSANEXT betweeen close cables
PSACR
Power Sum Attenuation to Crosstalk Ratio
A ratio in decibels that subtracts attenuation from PSNEXT loss
PSACRF
Power Sum Attenuation to Crosstalk Ratio Far End
A computation of unwated signal coupling from multiple transmitters at the near end into a pair measured at the far end
PSANEXT
Power Sum Alien Near End Crosstalk
The power sum of unwanted signal coupling from multiple disturbing end crosstalk pairs
Propagation Delay
Measurement of the time required for signal to travel from one end of the transmission path of the other end
Rayleigh Scattering
Scattering of light as it travels along an optical fiber
Return Loss
Measurement of the reflection of signal power resulting from the insertion of a device in a transmission line
SNR
Signal to Noise Ratio
The ratio between the amount of signal and noise
TDR
Time Domain Reflectometer
A testing device to measure length of cable and locate faults
What is required to perform field testing?
- Set of measurable transmission performance parameters
- necessary field test instruments
What should you do in situations where there are no predefined testing requirements for field testing?
Use the most applicable standard
What does a wire map test determine?
If the individual conductors in the cabling are connected correctly
Name seven errors that can be detected during a wire map test
- Continuity
- Shorts between conductors
- Transposed pairs
- Reversed pairs
- Split pairs
- Shield continuity
- Grounded conductor
True or False
Direct current loop resistance is required as an acceptance test for balanced twisted pair cabling
False
True or False
Characteristic impedance is not required as an acceptance test for balanced twisted pair cabling
True
What method is used to calculate the length of a balanced twisted pair cable?
The TDR method
What formula is used to calculate the maximum permissible length for a channel or permanent link?
(NVP x (round trip delay) x c x 110%) / 2
Name three variations in balanced twisted pair cable that can result in different propagation delays in the cable pairs
- Different twist rates
- Slightly different electrical characteristics
- Different dielectric materials
True or False
If a field test instrument uses the same NVP for all pairs in a balanced twisted pair cable, the reported length will be the same for each pair
False
What term refers to the time required for a signal to travel from one end of the transmission path to the other end?
Propagation Delay
What term describes the difference in propagation delay between the fastest and slowest pairs within the same cable sheath?
Delay Skew
What is the relationship between insertion loss in decibels and system performance?
The smaller the loss in decibels, the better the performance
What ratio is used to determine return loss?
The ratio of the reflected voltage to the incident signal voltage
What term is used to describe a ripple that appears in the curve when attenuation loss is plotted with frequency?
Insertion loss deviation
True or False
Insertion loss deviation is not required as an acceptance test
True
What is the relationship between the value of ACR-F in decibels and the performance of the cable link?
The higher the decibel level, the better the performance of the installed cable link
What does power sum crosstalk specify?
A combination of crosstalk from every source
What term refers to noise that is caused by adjacent data communication cables in the same bundle?
Alien Crosstalk
How are noise tests useful?
Troubleshooting problematic links or channels
Name two test parameters used to capture alien crosstalk coupling
- PSANEXT
- PSAACR-F
What types of faults are TDRs primarily used to identify?
Return Loss failures
Name the three configurations used for field testing horizontal balanced twisted pair cabling
- Channel
- Permanent Link
- Modular Plug Terminated Link (MPTL)
What does BICSI recommend take place before a permanent link is tested?
- Cable should be in place
- Both ends terminated
- Outlets in place
What is the ambient temperature used by field testing equipment?
68 F
What is the defined tester accuracy level for Category 5E (Class D) cable?
Level lle
What is the defined tester accuracy level for Category 6 (Class E) cable?
Level lll
What is the defined tester accuracy level for Category 6A (Class EA) cable?
Level llle
True or False
There are no defined accuracy levels for field testers to cover the requirements for class F products
True
What does a power sum measurement assume?
That all cables contribute to crosstalk
What is a bundled cable?
An assembly of two or more cables
Name two tests for backbone cable that exceeds horizontal length limits
- Continuity
- Wiremap
What type of testing requirements are used when field testing MUTOAs and CPs
Permant Link requirements
What should be used to demonstrate shield effectiveness of installed shielded cabling systems?
Alien Crosstalk test procedures
Name two applications for coaxial cabling
- Broadband applications
- Local area Networks (LANS) (legacy)
Name five types of tests that are performed on coaxial installations
- Direct current loop resistance
- Impedance
- Length
- TDR
- Noise
What type of coaxial cabling is the primary type of cabling used in distributed antenna systems?
50 ohm air dielectric coxial cable
Name the five functions that a 50 ohm cable tester can perform
- Continuity
- Attenuation
- TDR Impedance
- Voltage standing radio wave
- Provide pass or fail results
Which testing tool can be used to help identify areas that may need additional antennas to provide successful coverage?
Spectrum Analyzer
What term is used to describe loss in an optical fiber cable?
Attenuation
What is the recommended method for testing optical fiber attenuation?
Light source and power meter
What type of tester should be used to determine the length of an optical fiber cable?
OTDR
Name two methods for verifying polarity for an optical fiber cable
- OLTS
- Visible light source
What can result in the OTDR underestimating the loss for connectors and splices?
OTDR will underestime loss if it has an under-filled launch
How many cable ends need to be accessible to perform a test with an OTDR?
1
What is the purpose of using a launch cord with an OTDR?
Helps measure the insertion loss and reflectance of the first connection
What is the relationship between the length of a wavelength and the slope of a trace produced by an OTDR?
Shorter wavelengths produce a steeper slope
Name three measurements used for the minimum level of acceptance testing for optical fiber cabling
- Attenuation
- Length
- Polarity
Which reference method has the lowest level of uncertainty?
The one jumper reference method has the lowest level of uncertainty
How should premises optical fiber cable links be tested?
- Bidirectionally
- At their two corresponding wavelengths
What formula is used to calculate link attenuation?
Link Attenuation =
Cable Attenuation
+
Connector Attenuation
+
Splice Attenuation
What formular is used to calculate cable attenuation?
Cable Attenuation =
Attenuation Coefficient (dB/km)
x
Length
What formula is used to calculate connector attenuation?
Connector Attenuation (dB) =
Number of Connector Pairs (N)
x
Connector Loss (dB)
What foruma is used to calculate splice attenuation?
Splice Attenuation (dB) =
Number of Splices (S)
x
Splice Loss (dB)
What is the purpose of cable reel acceptance testing?
To ensure that the optical fiber cable is in good condition after the inventory, handling and shipping process
When does cable reel acceptance testing take place?
Within five working days of delivery
Why should the OLTS be allowed to normalize to the ambient temperature of the testing area before performing the test?
Helps to ensure consistent and repeatable results
What does the attenuation test measure?
Optical power loss between cable termination points
What are common issues that will result in system loss measurements being higher than the calculated link loss budget?
- Dirty connector end faces
- Connector issue
- Severe bend in cable
Where is end to end attenuation measured for multimode optical fiber cable?
At 850 nm and 1300 nm
Where is end to end attenuation measured for singlemode optical fiber cable?
At 1310 nm and 1550 nm
How long does the launch cord need to support and ODTR test?
Long enough to overcome the dead zone for the optical pulse width used
Name two simple safeguards that can be used to prevent service disruption in an optical fiber system
- Ensure connector care and cleanliness
- Check protection of system jumpers
Name four components that should be used to troubleshoot and restore optical fiber service as quickly as possibly
- Documentation
- Inspection and cleaning rating
- Test Equipment
- Troubleshooting plan
What is a potential issue with used wireless devices to communicate during testing?
Wireless devices may cause intereference with the first test instrument
How is a visible light source used?
To test and troubleshoot continuity of fiber
What happens if a tech uses a visual fault indicator to test a broken fiber cable?
The break will glow red during test
Describe how a strand identifier works
Inserts a macrobend into the fiber, allowing light escaping the cable to be detected
