VDV Testing and Certification 4 — Questions and Answers
Question 1: A technician is testing a coaxial video distribution system and finds the signal level at the last outlet is 6 dB below the minimum required level. What is the most appropriate corrective action?
- Replace all coaxial cable with higher-gauge cable
- Install an amplifier or distribution amplifier at an appropriate point in the signal chain (Correct answer)
- Increase the source output by 12 dB
- Terminate unused outlets with 75-ohm terminators
Correct answer: Install an amplifier or distribution amplifier at an appropriate point in the signal chain
Installing a distribution amplifier at a strategic point in the signal chain compensates for cable and splitter losses to restore adequate signal levels at all outlets.
Question 2: What does it mean when a cable tester reports an 'open' fault 23 meters from the near end?
- There is a short circuit at 23 meters
- A conductor has a break or disconnection at approximately 23 meters (Correct answer)
- The cable is too long at 23 meters
- The impedance increases at 23 meters
Correct answer: A conductor has a break or disconnection at approximately 23 meters
An open fault indicates a break in the conductor at the reported distance, preventing signal continuity beyond that point.
Question 3: When performing Tier 2 fiber optic testing, what additional measurement does it provide beyond Tier 1?
- Connector end-face cleanliness
- OTDR traces showing event locations and individual span losses (Correct answer)
- Fiber core diameter verification
- Wavelength accuracy of the light source
Correct answer: OTDR traces showing event locations and individual span losses
Tier 2 testing adds OTDR measurements to the basic Tier 1 insertion loss results, providing detailed event location, splice loss, and connector loss information along the fiber span.
Question 4: A VDV technician must certify a Cat 5e horizontal link for Gigabit Ethernet. Which pair of test parameters is most critical to verify?
- Wiremap and cable length only
- Insertion loss and NEXT at a minimum, as part of a full suite per TIA-568-C.2 (Correct answer)
- DC resistance and capacitance
- Only propagation delay
Correct answer: Insertion loss and NEXT at a minimum, as part of a full suite per TIA-568-C.2
Full certification for Gigabit Ethernet on Cat 5e requires a complete test suite including insertion loss, NEXT, ELFEXT, return loss, and propagation delay per TIA-568-C.2.
Question 5: What is the significance of the 'loss budget' in a fiber optic link design and testing?
- The cost allocation for fiber materials
- The maximum allowable total attenuation from source to receiver for reliable operation (Correct answer)
- The number of splices permitted per 100 meters
- The minimum transmit power required
Correct answer: The maximum allowable total attenuation from source to receiver for reliable operation
The loss budget defines the maximum total dB loss a fiber link can have while still allowing the receiver to operate reliably, accounting for all connectors, splices, and cable attenuation.
Question 6: During structured cabling certification, what is the maximum permanent link length for Cat 6 horizontal cabling per TIA-568-C.2?
- 90 meters (Correct answer)
- 100 meters
- 85 meters
- 70 meters
Correct answer: 90 meters
The permanent link (horizontal cable only, excluding patch cords) is limited to 90 meters, with the remaining 10 meters allocated for equipment and work area patch cords in the 100-meter channel.
Question 7: A technician is certifying a fiber installation and the OTDR shows a splice loss of 0.4 dB at a fusion splice. How does this compare to industry standards?
- It exceeds the typical 0.3 dB maximum for fusion splices (Correct answer)
- It is within the acceptable range for fusion splices
- It is too low and indicates a measurement error
- It is only acceptable for single-mode fiber
Correct answer: It exceeds the typical 0.3 dB maximum for fusion splices
The industry standard for fusion splice loss is typically 0.3 dB maximum, so a 0.4 dB reading exceeds this limit and may require the splice to be redone.
VDV Testing and Certification 4
A technician is testing a coaxial video distribution system and finds the signal level at the last outlet is 6 dB below the minimum required level.
What is the most appropriate corrective action?