Huawei H35-210_V2.5 Practice Test - Questions Answers, Page 3

GPON Overview :

GPON (Gigabit Passive Optical Network) is a fiber-optic access technology standardized by the ITU-T (International Telecommunication Union) under the G.984.x series of standards.

It is not based on Ethernet but uses its own framing structure called GEM (GPON Encapsulation Method) for data transmission.

IEEE 802.3ah :

IEEE 802.3ah is the standard for EPON (Ethernet Passive Optical Network) , which is a competing technology to GPON.

EPON uses Ethernet frames for data transmission and is standardized by the IEEE, unlike GPON, which is standardized by ITU-T.

Why FALSE?

The statement incorrectly associates GPON with IEEE 802.3ah, which applies to EPON, not GPON.

Thus, the correct answer is B .

HCIA Huawei ACCESS Official Documentation , Chapter: GPON vs. EPON.

ITU-T G.984.x Standards for GPON .

GPON Wavelengths :

GPON networks use specific wavelengths for upstream and downstream transmission:

Downstream (OLT to ONU) : 1490 nm.

Upstream (ONU to OLT) : 1310 nm.

Optional CATV overlay : 1550 nm (used for video services).

Why 1490 nm?

The ITU-T G.984.x standards specify 1490 nm as the wavelength for downstream data transmission in GPON networks. This wavelength is chosen for optimal performance in fiber-optic communication.

Other Options :

850 nm : Used in multimode fiber for short-distance communication, not in GPON.

1310 nm : Used for upstream transmission in GPON.

1550 nm : Optional wavelength for CATV overlay, not for standard downstream data.

Thus, the correct answer is A .

HCIA Huawei ACCESS Official Documentation , Chapter: GPON Wavelengths.

ITU-T G.984.x Standards for GPON .

Downstream Transmission :

In GPON, downstream data is broadcast to all ONUs. However, each ONU only processes the data intended for it, identified by a unique identifier (ONU ID).

Upstream Transmission :

In the upstream direction, GPON uses TDMA (Time Division Multiple Access) to prevent collisions. Each ONU transmits data during its allocated time slot, and the optical splitter does not allow data from one branch fiber to interfere with another.

Why FALSE?

The second part of the statement is incorrect. Data from one branch fiber cannot be received by another branch fiber due to the TDMA mechanism and the design of the passive optical splitter.

Thus, the correct answer is B .

HCIA Huawei ACCESS Official Documentation , Chapter: GPON Upstream and Downstream Transmission.

GPON System Architecture by Huawei.

PON Network Components :

OLT (Optical Line Terminal) : Central office equipment that connects to the core network.

ODN (Optical Distribution Network) : Consists of optical fibers, splitters, and connectors that distribute signals between the OLT and ONUs.

ONU (Optical Network Unit) : End-user equipment that connects to customer devices.

OAM (Operations, Administration, and Maintenance) :

OAM refers to a set of tools and protocols used for managing and maintaining the network. It is not a physical component of the PON system.

Why A?

OAM is a function or process, not a physical part of the PON network system.

Thus, the correct answer is A .

HCIA Huawei ACCESS Official Documentation , Chapter: PON Network Components.

GPON System Architecture by Huawei.

DBA (Dynamic Bandwidth Allocation) :

DBA is a mechanism in GPON networks that dynamically allocates upstream bandwidth among ONUs based on their traffic demands.

Functions of DBA :

Improves upstream bandwidth utilization : DBA ensures efficient use of the limited upstream bandwidth by allocating it dynamically to ONUs as needed.

Does not increase total upstream bandwidth : The total upstream bandwidth of a PON port is fixed and determined by the hardware. DBA optimizes how this bandwidth is used.

Does not affect downstream bandwidth : Downstream bandwidth is shared via broadcasting and is not managed by DBA.

Does not add more ONUs : The number of ONUs supported by a PON port depends on hardware capacity, not DBA.

Why C?

DBA improves the efficiency of upstream bandwidth utilization by dynamically allocating resources.

Thus, the correct answer is C .

HCIA Huawei ACCESS Official Documentation , Chapter: GPON DBA Mechanism.

GPON Dynamic Bandwidth Allocation by Huawei.

XGS-PON Wavelengths :

XGS-PON (10-Gigabit Symmetric Passive Optical Network) uses specific wavelengths for upstream and downstream transmission:

Downstream (OLT to ONU) : 1577 nm.

Upstream (ONU to OLT) : 1270 nm.

Why 1577 nm?

The ITU-T G.9807.1 standard specifies 1577 nm as the downstream wavelength for XGS-PON. This wavelength is chosen to avoid interference with GPON, which uses 1490 nm for downstream transmission.

Other Options :

1490 nm : Used for downstream transmission in GPON, not XGS-PON.

1310 nm : Used for upstream transmission in GPON, not XGS-PON.

1290 nm : Not a standard wavelength in PON technologies.

Thus, the correct answer is C .

HCIA Huawei ACCESS Official Documentation , Chapter: XGS-PON Wavelengths.

ITU-T G.9807.1 Standards for XGS-PON .

GPON vs. XGS-PON :

GPON : Provides asymmetric bandwidth (2.5 Gbps downstream, 1.25 Gbps upstream) and supports up to 128 ONUs per PON port.

XGS-PON : Provides symmetric bandwidth (10 Gbps upstream and downstream) and supports up to 256 ONUs per PON port.

ODN Compatibility :

XGS-PON operates over the same ODN (Optical Distribution Network) as GPON, meaning no changes are required to the existing fiber infrastructure.

XGS-PON uses different wavelengths (1577 nm downstream, 1270 nm upstream) to coexist with GPON on the same ODN using wavelength division multiplexing (WDM).

Why TRUE?

XGS-PON supports higher bandwidth and more users while maintaining compatibility with the existing GPON ODN architecture.

Thus, the correct answer is A .

HCIA Huawei ACCESS Official Documentation , Chapter: GPON vs. XGS-PON.

ITU-T G.9807.1 Standards for XGS-PON .

Let us analyze each statement:

Option A :

Correct : WDM1r multiplexers can be flexibly deployed close to the Central Office (CO) or closer to the user, depending on network design requirements.

Option B :

Incorrect : While GPON and XGS-PON share the same ODN architecture, simply changing the optical modules on an ONU is insufficient to support XGS-PON. The ONU hardware and software must also be compatible with XGS-PON standards.

Option C :

Incorrect : The deployment of WDM1r multiplexers introduces additional optical loss, which must be accounted for in the calculation of optical link attenuation.

Option D :

Correct : GPON (1490 nm downstream, 1310 nm upstream) and XGS-PON (1577 nm downstream, 1270 nm upstream) use non-overlapping wavelengths, allowing them to coexist on the same ODN using WDM.

Thus, the incorrect statements are B and C .

HCIA Huawei ACCESS Official Documentation , Chapter: GPON and XGS-PON Coexistence.

ITU-T G.9807.1 Standards for XGS-PON .

ADSL Interleave Mode :

Interleave mode is used in ADSL to improve error correction by interleaving data bits before transmission.

This process introduces additional latency (delay) but enhances stability by reducing the impact of impulse noise.

Why B?

Better stability : Interleaving spreads errors across multiple frames, making it easier to correct them.

Longer delay : The interleaving process adds latency due to the time required to reorder data bits.

Other Options :

A : Incorrect because interleave mode improves stability, not worsens it.

C : Incorrect because interleave mode increases delay, not reduces it.

D : Incorrect because interleave mode improves stability.

Thus, the correct answer is B .

HCIA Huawei ACCESS Official Documentation , Chapter: ADSL Modes.

ADSL Interleaving and Fast Path by Huawei.