CTA Broadband & Access Network Technologies 2 — Questions and Answers
Question 1: Which passive optical network (PON) standard is most widely deployed for fiber-to-the-home (FTTH) services?
- APON (ATM PON)
- BPON (Broadband PON)
- EPON (Ethernet PON)
- GPON (Gigabit PON) (Correct answer)
Correct answer: GPON (Gigabit PON)
GPON (Gigabit Passive Optical Network), defined by ITU-T G.984, is the most widely deployed FTTH standard worldwide due to its high capacity, efficiency, and support for triple-play services.
Question 2: What wavelength is used for downstream transmission in a standard GPON deployment?
- 1310 nm
- 1490 nm (Correct answer)
- 1550 nm
- 1625 nm
Correct answer: 1490 nm
In GPON, the 1490 nm wavelength carries downstream (OLT to ONU) traffic, while 1310 nm is used for upstream transmission from the ONU to the OLT.
Question 3: What is the maximum downstream data rate defined in the GPON standard (ITU-T G.984)?
- 622 Mbps
- 1.25 Gbps
- 2.5 Gbps (Correct answer)
- 10 Gbps
Correct answer: 2.5 Gbps
The GPON standard specifies a maximum downstream rate of 2.488 Gbps (approximately 2.5 Gbps) and an upstream rate of 1.244 Gbps.
Question 4: In an FTTx deployment where fiber runs to a street cabinet and existing copper carries the signal to individual homes, which architecture is this?
- FTTH (Fiber to the Home)
- FTTB (Fiber to the Building)
- FTTC (Fiber to the Cabinet/Curb) (Correct answer)
- FTTP (Fiber to the Premises)
Correct answer: FTTC (Fiber to the Cabinet/Curb)
FTTC (Fiber to the Cabinet or Curb) runs fiber from the central office to a street cabinet near the customer, then uses existing copper (often VDSL2) for the short remaining distance to the home.
Question 5: What is XG-PON (10G-PON), standardized as ITU-T G.987?
- A passive optical network standard providing 10 Gbps downstream and 2.5 Gbps upstream (Correct answer)
- An experimental wireless broadband protocol for rural areas
- A cable TV standard for 10 GHz millimeter-wave operation
- A DSL bonding standard targeting 10 Gbps aggregate bandwidth
Correct answer: A passive optical network standard providing 10 Gbps downstream and 2.5 Gbps upstream
XG-PON (10-Gigabit-capable PON), defined in ITU-T G.987, delivers 10 Gbps downstream and 2.5 Gbps upstream over the same passive fiber infrastructure used by GPON.
Question 6: Which access network technology uses a hybrid combination of fiber for the backbone and coaxial cable for the final distribution to subscribers?
- FTTH (Fiber to the Home)
- HFC (Hybrid Fiber-Coaxial) (Correct answer)
- VDSL2 (Very High Speed DSL 2)
- ADSL2+ (Asymmetric DSL 2+)
Correct answer: HFC (Hybrid Fiber-Coaxial)
HFC (Hybrid Fiber-Coaxial) networks use fiber optic cable from the headend to neighborhood nodes and coaxial cable from nodes to individual subscriber premises, combining the strengths of both media.
Question 7: In a GPON network, what is the maximum logical split ratio supported by the standard?
- 1:16
- 1:32
- 1:64
- 1:128 (Correct answer)
Correct answer: 1:128
The GPON standard (ITU-T G.984) supports a maximum logical split ratio of 1:128, meaning one OLT port can serve up to 128 ONUs, though typical deployments use 1:32 or 1:64 for bandwidth management.
CTA Broadband & Access Network Technologies 2
Which passive optical network (PON) standard is most widely deployed for fiber-to-the-home (FTTH) services?