The correct answers areClass B+andClass C+. These optical module classes are widely used in commercial GPON deployments due to their balance of performance, cost, and reliability.
* Class B+:Supports transmission distances up to20 kmand is commonly used in urban and suburban areas. It provides sufficient power budget for most residential and small business applications.
* Class C+:Supports longer distances (up to40 km) and higher split ratios, making it idealfor rural or remote areas where extended reach is required.
Other options:
* Class D:Not a standard classification for GPON optical modules.
* Class E and F:These classifications do not exist in current GPON standards.
The choice between Class B+ and Class C+ depends on the specific deployment scenario, including distance, split ratio, and environmental conditions.

TheGPON (Gigabit Passive Optical Network)standard, defined by the ITU-T G.984 specification, supports asymmetric data rates for upstream and downstream traffic. Specifically:
* Downstream Bitrate:2.5 Gbps
* Upstream Bitrate:1.25 Gbps
The higher downstream bitrate reflects the typical usage pattern of internet services, where users consume more data (e.g., streaming videos) than they upload. GPON uses Time Division Multiplexing (TDM) to manage data transmission between the OLT and multiple ONUs.
For higher bandwidth requirements, advanced standards like XG-PON (10 Gbps downstream) or NG-PON2 (multi-wavelength support) are available.
References:
* ITU-T G.984 Standard - GPON Architecture
* Huawei GPON Technical Documentation