OSP Fiber Optic & Copper Cabling Systems 3 — Questions and Answers
Question 1: A fiber optic cable rated as 'OFNR' can be installed in which of the following locations?
- Plenum spaces above suspended ceilings
- Riser shafts between floors (Correct answer)
- Direct burial in outdoor conduit
- Aerial lashed to strand
Correct answer: Riser shafts between floors
OFNR (Optical Fiber Non-conductive Riser) is rated for vertical runs in riser shafts where fire spread between floors is the primary concern.
Question 2: When calculating copper cable resistance for OSP loop design, which factor has the GREATEST effect on loop resistance?
- Insulation material type
- Conductor gauge (AWG) (Correct answer)
- Cable sheath color
- Number of pairs in the cable
Correct answer: Conductor gauge (AWG)
Conductor gauge (AWG) is the dominant factor; smaller AWG numbers indicate larger wire diameters with lower resistance per unit length.
Question 3: In wavelength-division multiplexing (WDM) fiber systems, what does 'channel spacing' refer to?
- Physical distance between fiber strands in a cable
- Frequency or wavelength separation between adjacent optical carriers (Correct answer)
- Time interval between data packets on a single fiber
- Gap between splice enclosures on a route
Correct answer: Frequency or wavelength separation between adjacent optical carriers
Channel spacing defines the frequency (in GHz) or wavelength (in nm) separation between WDM channels to prevent inter-channel interference.
Question 4: What is the purpose of an 'optical time-domain reflectometer' (OTDR) launch cable?
- To extend the fiber span beyond normal operating distance
- To eliminate the dead zone at the beginning of a trace near the OTDR port (Correct answer)
- To convert multimode signals to single-mode for testing
- To boost signal power during testing
Correct answer: To eliminate the dead zone at the beginning of a trace near the OTDR port
A launch cable (typically 100-500 m) moves the OTDR's near-end dead zone away from the fiber under test, allowing the first splice or connector to be accurately measured.
Question 5: Which copper cable test parameter measures the ability of a cable to reject unwanted signals from external electromagnetic sources?
- Return loss
- Propagation delay
- Transfer impedance (shield effectiveness) (Correct answer)
- Insertion loss
Correct answer: Transfer impedance (shield effectiveness)
Transfer impedance (or shield effectiveness) quantifies how well a cable's shield prevents external EMI from coupling onto the signal conductors.
Question 6: For OSP fiber installations, what is the minimum bend radius typically specified during cable installation (under tension)?
- 5x the cable outer diameter
- 10x the cable outer diameter
- 20x the cable outer diameter (Correct answer)
- 50x the cable outer diameter
Correct answer: 20x the cable outer diameter
During installation under tension, most OSP fiber cables require a minimum bend radius of 20 times the cable outer diameter to prevent fiber microbending and damage.
Question 7: A copper telephone cable with 'PE' sheath designation is designed primarily for:
- Plenum-rated indoor use
- Direct burial or conduit in outdoor environments (Correct answer)
- Riser vertical runs between floors
- Aerial lashing above ground
Correct answer: Direct burial or conduit in outdoor environments
PE (polyethylene) sheathing provides excellent moisture resistance and UV stability, making it the standard choice for direct burial and conduit-installed OSP copper cables.
OSP Fiber Optic & Copper Cabling Systems 3
A fiber optic cable rated as 'OFNR' can be installed in which of the following locations?