The split ratio refers to the number of ONUs connected to a single PON port on the OLT through optical splitters. In the backbone of modern Fiber-to-the-Home (FTTH) networks, optical splitters serve as the unsung heroes that enable cost-efficient connectivity for millions of subscribers. By dividing a single optical signal from a central Optical Line Terminal (OLT) into multiple outputs for Optical Network. In fiber optic networks, especially in FTTx deployments, the number of Optical Network Units (ONUs) that a single PON port on an Optical Line Terminal (OLT) can support directly affects network planning, cost-efficiency, and service scalability. In this article, we'll explain the concept of split. To deploy a successful FTTH network, one must consider factors such as the choice of splitter, splitting level, and splitting ratio. Its single-fiber bidirectional transmission mechanism employs WDM, where downstream traffic adopts broadcast mode (1490nm wavelength), and upstream traffic uses TDMA. In FTTH architectures, splitters determine how optical power is distributed from a central feeder fiber to multiple subscriber branches. Split ratio selection directly affects power margin, network scalability, and fault isolation complexity.