CTA Fiber Optics & Physical Layer Technologies 2 — Questions and Answers
Question 1: What is the maximum reach of 10GBASE-LR (10 Gigabit Ethernet over single-mode fiber) per IEEE 802.3ae?
- 100 meters
- 550 meters
- 10 kilometers (Correct answer)
- 40 kilometers
Correct answer: 10 kilometers
10GBASE-LR uses 1310 nm light over single-mode fiber and is specified for reaches up to 10 km per IEEE 802.3ae.
Question 2: In a Passive Optical Network (PON), what device splits the optical signal from the central office to multiple subscriber premises?
- EDFA (Erbium-Doped Fiber Amplifier)
- Optical Line Terminal (OLT)
- Optical splitter (Correct answer)
- Wavelength router
Correct answer: Optical splitter
A passive optical splitter divides the downstream optical signal from the OLT to multiple ONTs at subscriber locations without requiring electrical power.
Question 3: What is the maximum downstream bandwidth per PON port in XGS-PON (10G Symmetrical PON)?
- 1 Gbps
- 2.5 Gbps
- 10 Gbps (Correct answer)
- 25 Gbps
Correct answer: 10 Gbps
XGS-PON provides 10 Gbps symmetrical (downstream and upstream) bandwidth per PON port, per ITU-T G.9807.1.
Question 4: What causes optical back-reflection in a fiber link, and how is it typically mitigated?
- Dispersion at connectors; mitigated by chromatic dispersion compensators
- Fresnel reflection at fiber end faces and connectors; mitigated using angled physical contact (APC) connectors or index-matching gel (Correct answer)
- Scattering in the fiber core; mitigated by EDFA amplifiers
- Polarization mode dispersion; mitigated using polarization controllers
Correct answer: Fresnel reflection at fiber end faces and connectors; mitigated using angled physical contact (APC) connectors or index-matching gel
Fresnel reflections occur at any glass-air interface (connectors, splices) and can disrupt laser sources; APC connectors reduce this by angling the end face to redirect reflections.
Question 5: In DSL technology, what does the term 'attenuation' refer to in the context of loop length?
- The reduction in signal strength as the electrical signal travels over copper pairs, which increases with loop length (Correct answer)
- The noise added by telephone switching equipment
- The delay introduced by DSL modems
- The frequency filtering applied by the DSLAM
Correct answer: The reduction in signal strength as the electrical signal travels over copper pairs, which increases with loop length
DSL performance degrades with loop length because the copper pair attenuates (weakens) the high-frequency signals, reducing achievable speed as distance from the DSLAM increases.
Question 6: What type of cable is used in most US residential CATV (cable TV) and HFC networks to connect homes to the distribution network?
- Twisted pair copper (UTP)
- Single-mode fiber to the premises
- RG-6 coaxial cable (Correct answer)
- Multimode fiber (OM3)
Correct answer: RG-6 coaxial cable
RG-6 coaxial cable is the standard drop cable used in HFC (Hybrid Fiber Coaxial) networks to connect homes to the coaxial distribution plant.
CTA Fiber Optics & Physical Layer Technologies 2
What is the maximum reach of 10GBASE-LR (10 Gigabit Ethernet over single-mode fiber) per IEEE 802.3ae?