OSP Fiber Optic & Copper Cabling Systems 5 — Questions and Answers
Question 1: In a DWDM (Dense Wavelength Division Multiplexing) OSP system, the ITU-T G.694.1 grid defines channel spacing at which standard interval?
- 50 GHz or 100 GHz (Correct answer)
- 10 nm or 20 nm
- 1310 nm and 1550 nm only
- OC-3 and OC-12 intervals
Correct answer: 50 GHz or 100 GHz
ITU-T G.694.1 defines the DWDM frequency grid with standard channel spacings of 12.5, 25, 50, and 100 GHz centered on 193.1 THz.
Question 2: When a fiber cable manufacturer specifies 'cabled fiber attenuation' versus 'uncabled fiber attenuation,' the cabled value is typically:
- Lower because the cable protects the fiber from stress
- The same since cabling does not affect optical properties
- Slightly higher due to microbending induced by cabling materials and process (Correct answer)
- Significantly higher due to connector insertion loss included in the spec
Correct answer: Slightly higher due to microbending induced by cabling materials and process
Cabling processes can induce microbending stress on fibers, slightly increasing attenuation compared to the bare fiber measurement; this is why manufacturers specify both values.
Question 3: A copper cable's 'characteristic impedance' is important in high-frequency applications because:
- It determines the maximum current the cable can safely carry
- Mismatched impedance causes signal reflections that degrade performance (Correct answer)
- It sets the maximum voltage the insulation can withstand
- It controls the resistance heating of conductors at load current
Correct answer: Mismatched impedance causes signal reflections that degrade performance
Impedance mismatches at cable terminations or splices cause signal reflections (return loss) that can corrupt data in high-speed copper transmission systems.
Question 4: Which OSP fiber cable type is specifically designed to be directly installed in duct or conduit without requiring a pull rope, due to its low-friction outer jacket?
- ADSS (All-Dielectric Self-Supporting) cable
- Figure-8 self-supporting cable
- Microduct blown fiber cable (Correct answer)
- Armored direct-burial cable
Correct answer: Microduct blown fiber cable
Microduct blown fiber (air-blown fiber) uses compressed air to float very lightweight fiber bundles through small conduits at high speed without mechanical pulling tension.
Question 5: For outside plant copper cable, what does the term 'loop resistance' mean and what is its significance?
- The resistance of the cable shield, critical for lightning protection design
- The total DC resistance of the two conductors of a pair end-to-end, critical for powering and signaling devices (Correct answer)
- The insulation resistance between conductors, critical for crosstalk performance
- The resistance of the splice connection, critical for signal continuity
Correct answer: The total DC resistance of the two conductors of a pair end-to-end, critical for powering and signaling devices
Loop resistance is the sum of resistance of both conductors in a pair measured end-to-end, determining whether sufficient current can flow to power devices like telephone instruments or DSL equipment.
Question 6: What is the primary purpose of 'dispersion-shifted fiber' (DSF, ITU-T G.653) in long-haul OSP networks?
- To reduce attenuation below 0.1 dB/km at 1550 nm
- To shift the zero-dispersion wavelength from 1310 nm to 1550 nm for use with low-loss EDFA amplifiers (Correct answer)
- To support multimode transmission for campus backbone applications
- To provide bend-insensitive performance in tight-buffer indoor cables
Correct answer: To shift the zero-dispersion wavelength from 1310 nm to 1550 nm for use with low-loss EDFA amplifiers
DSF is engineered to have zero chromatic dispersion at 1550 nm, the wavelength window where erbium-doped fiber amplifiers (EDFAs) operate and where fiber attenuation is lowest.
Question 7: When splicing a 96-fiber OSP cable, a technician uses a color-coded ribbon or tube identification system. What standard governs fiber color coding in the US?
- ANSI/TIA-598 (Correct answer)
- IEEE 802.3
- ITU-T G.652
- Bellcore TR-NWT-000418
Correct answer: ANSI/TIA-598
ANSI/TIA-598 defines the standard color code sequence (blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, aqua) used for fiber identification in US OSP cables.
OSP Fiber Optic & Copper Cabling Systems 5
In a DWDM (Dense Wavelength Division Multiplexing) OSP system, the ITU-T G.694.1 grid defines channel spacing at which standard interval?