FTTB(fiber to the building) Solution
FTTB Solution is Fiber To The Building Solution. Here we explain about Fiber To The Building+ONU solution.
FTTB+ONU refers to the XPON solution based on passive optical networks. Currently, the main applications are EPON and GPON.

1.Network Layout

1.1 OLT Planning
The OLT is connected to the BRAS of the IP metropolitan area network through the GE interface. When the resources of the BRAS port are insufficient, the OLT can connect to the BRAS through Ethernet cascading or increase the aggregation switch. The cascading level should not exceed 1 level. It is connected to the optical multiplexer through a single fiber, and is split by a splitter to be connected to a plurality of ONUs.

1.2 Planning of the optical network
The use of XPON to build a network requires a large amount of fiber. This requires careful planning of the fiber. Otherwise, it will result in waste of investment and difficulty in using the fiber in the future.
When planning the optical fiber network, it is necessary to use the OLT as the basis, combine the existing optical fiber resources, make overall plans, and implement according to the user development. In the planning, we should focus on trunk cable planning, including the capacity of the trunk cable, the path, the optical junction box and the location of the optical splitter, in order to facilitate the construction of the distribution cable in the future, so as to easily access the target user group.

1.3 Splitting level planning
In order to ensure the network quality and a certain transmission distance, the passive optical splitter should adopt the first-level splitting or two-level splitting, that is, the splitter can be set up to two levels. In principle, no third or third level splitting is used.
2.Splitter Selection and Setting

2.1 SplitRratio Selection
The common split ratios of the splitter are: 1:2, 1:4, 1:8, 1:16, 1:32. In practice, according to the number of ONUs connected to the splitter, and considering the appropriate reservation, the splitter of the corresponding split ratio is selected. When two stages splitting is used, the product of the split ratio of the first stag and the second stage should be no larger than the maximum split ratio (32 for EPON and 64 for GPON).

2.2 Splitter settings
In order to facilitate the entry and exit of the optical cable, the optical splitter can be disposed in the cell room, fiber optical cabinet, Fiber optical distribution frame(ODF), fiber cable closure and a weak electric well etc.