FTTH and Fiber Broadband: Architecture and Deployment
Architecture
FTTH delivers fiber to the home using PON or point-to-point active Ethernet. In a typical GPON/XGS-PON network, the OLT sits in the central office or headend, feeder fiber runs to a splitter (often in a street cabinet or pedestal), distribution fiber reaches access points, and drop cable enters the home to an ONT/ONU. Splitters may be centralized or distributed; cascaded splitters increase loss. Know the roles of OLT, ONT, splitter, and passive infrastructure.
Deployment and installation
Understand feeder/distribution/drop segments, aerial and buried drop methods, and hardware such as closures, terminals, and customer premises boxes. Preconnectorized drop cables speed installation but require careful handling. Inside the home, the ONT needs power and a location that supports Wi-Fi and service wiring. Testing includes optical loss and power at the ONT; installers verify the receive level is within the ONT's range.
Service and operations
Know that PON is shared downstream and upstream with scheduling, that WDM separates wavelengths (e.g., 1490 nm downstream, 1310 nm upstream, 1550 nm video overlay), and that troubleshooting distinguishes fiber faults from ONT power or provisioning issues. Traps: exceeding splitter ratios or budget; confusing downstream and upstream wavelengths; and forgetting that a dirty connector at the ONT can look like a dead drop.
Worked example
A GPON design uses a 1:32 splitter (about 17.5 dB) plus 8 km feeder/distribution at 0.35 dB/km (2.8 dB), 4 connectors (2.0 dB), and 2 splices (0.2 dB), totaling 22.5 dB. If the class budget is 28 dB, margin is 5.5 dB, which is acceptable; a 1:64 splitter would add about 3.5 dB and reduce margin to about 2 dB, likely too tight.