DCI Testing and Certification 3 — Questions and Answers
Question 1: Which fiber optic test method uses a light source and power meter to measure end-to-end insertion loss?
- OTDR testing
- Optical Loss Test Set (OLTS) method (Correct answer)
- Visual Fault Locator (VFL) method
- Chromatic Dispersion testing
Correct answer: Optical Loss Test Set (OLTS) method
The Optical Loss Test Set (OLTS) method, also called the light source and power meter (LSPM) method, is the standard bidirectional method for certifying fiber insertion loss.
Question 2: What TIA standard defines the required test methods and pass/fail criteria for copper cabling certification?
- TIA-568-C.2 (Correct answer)
- TIA-942
- TIA-606
- TIA-569
Correct answer: TIA-568-C.2
TIA-568-C.2 (Balanced Twisted-Pair Telecommunication Cabling and Components Standard) specifies transmission performance and field test requirements for copper cabling.
Question 3: A cable technician measures propagation delay and delay skew. What is delay skew?
- The total one-way propagation time from transmitter to receiver
- The difference in propagation delay between the fastest and slowest pair in a cable (Correct answer)
- The phase difference between the two conductors of a single pair
- The time required for an OTDR pulse to travel to the end of a fiber
Correct answer: The difference in propagation delay between the fastest and slowest pair in a cable
Delay skew is the difference in signal travel time between the fastest and slowest pairs in a cable, which must be within limits to ensure proper signal reconstruction.
Question 4: When certifying a fiber link per TIA-526-14, the bidirectional average insertion loss is required. Why are measurements taken in both directions?
- Fiber has different loss in each direction due to light polarity
- Connector and splice losses can vary depending on the direction light travels (Correct answer)
- The OTDR requires two passes to eliminate dead zones
- To double the effective test distance
Correct answer: Connector and splice losses can vary depending on the direction light travels
Connector losses are directional because the physical alignment of fiber cores at a mated pair can differ depending on which way light travels through the connection.
Question 5: What is the significance of the 'headroom' value reported by a cable certification tester?
- The remaining cable length before the 90-meter limit is reached
- The margin between the measured result and the pass/fail limit (Correct answer)
- The number of additional connections permitted on the link
- The difference between installed cable category and the required category
Correct answer: The margin between the measured result and the pass/fail limit
Headroom indicates how far the measured performance is above or below the specification limit, with positive values indicating a margin of safety above the minimum requirement.
Question 6: Which connector type is standardized for 10-Gigabit Ethernet over Category 6A cabling in commercial buildings?
- RJ-11
- RJ-45 (8P8C) (Correct answer)
- LC duplex
- BNC
Correct answer: RJ-45 (8P8C)
The RJ-45 (8-position 8-contact) connector is the standardized interface for 10GBASE-T and all other structured cabling copper applications per TIA-568.
Question 7: An OTDR test shows a 'non-reflective event' with a loss spike but no reflection peak. What does this typically indicate?
- A connector end-face contamination
- A mechanical or fusion splice (Correct answer)
- A fiber break open to air
- A defective pigtail
Correct answer: A mechanical or fusion splice
Non-reflective events such as fusion splices cause signal loss without significant back-reflection, unlike connectors or breaks which produce Fresnel reflections.
DCI Testing and Certification 3
Which fiber optic test method uses a light source and power meter to measure end-to-end insertion loss?