Optical splitter and ONU

In a PON system, the ONU connects to an optical splitter via the Optical Distribution Network (ODN), allowing a single OLT to serve multiple end users efficiently. Overview of the ConnectionIn a Passive Optical Network (PON), the Optical Line Terminal (OLT) at the service provider's central office sends optical signals downstream through the Optical Distribution Network (ODN).

The OD

N includes optical fibers and passive optical splitters, which divide the signal from the OLT to multiple ONUs (Optical Network Units) or ONTs (Optical Network Terminals) near end users.

The ON

U converts the optical signal into electrical signals for user devices and aggregates upstream data back to the OLT. Role of the Optical SplitterThe optical splitter is a passive device that distributes the optical signal from a single fiber to multiple fibers, enabling a point-to-multipoint topology. Splitters can have various ratios, such as 1: 32 or 1: 64, depending on the number of ONUs served.

In some deployments, primary splitting connects the OLT directly to ONUs via a single splitter, while secondary splitting uses a cascade of two splitters to extend coverage in larger or rural areas.

Connection Methods

The OL

T connects to the optical splitter through a single optical fiber. The splitter then connects to multiple ONUs, each receiving a portion of the optical signal. Downstream data is broadcast to all ONUs, with each ONU extracting its intended data using identifiers like GEM port IDs in GPON systems.

Upstream data from ONUs is time-division multiplexed (TDMA) to avoid collisions and sent back to the OLT.

Placement and Deployment

Splitters are typically installed in fiber distribution boxes (FDBs), at intersections of optical paths, or in rack-mounted 1U boxes for compact deployment. The choice of splitting ratio and placement depends on network density: urban areas often use primary splitting for cost efficiency, while rural areas may use secondary splitting to cover wider distances.

Summary

The ON

U connects to the optical splitter as part of the ODN, enabling efficient downstream distribution and upstream aggregation of data. The splitter's passive nature allows multiple ONUs to share a single OLT port, optimizing fiber usage and network scalability. This architecture is fundamental to GPON, EPON, and other PON technologies.