Optical splitter in network

Optical splitters enable cost-efficient, scalable PON networks by dividing a single optical signal from the OLT to multiple ONTs, using centralized or distributed architectures with various split ratios.

Overview of Optical Splitters

Optical splitters are passive devices that divide a single input optical signal into multiple outputs or combine multiple signals into one, without requiring power. They are essential in Passive Optical Networks (PON), allowing one Optical Line Terminal (OLT) to serve multiple Optical Network Terminals (ONTs), reducing fiber deployment costs and improving scalability . Key performance metrics include:

• Split Ratio: Determines how the input signal is divided (e.g., 1×4, 1×8, 1×32, 1×64). Higher ratios increase the number of users but also increase insertion loss .
• Insertion Loss: Signal attenuation caused by splitting; must be managed to maintain network reach and quality .
• Uniformity: Consistency of output power across all ports, critical for reliable service . Two main splitter types are used:
• FBT (Fused Biconical Taper) Splitters: Cost-effective, suitable for small splits like 1:2 or 1:4 .
• PLC (Planar Lightwave Circuit) Splitters: Highly uniform, ideal for large splits like 1:32 or 1:64, and reduce insertion loss for high-performance networks .

Splitter Architectures

Centralized Splitting

• A single-stage splitter is deployed near the OLT or central office.
• Structure: OLT → Optical Splitter → ONT
• Advantages: Easy management, flexible customer assignment via jumpers, and simplified maintenance .
• Best for networks with predictable subscriber distribution and centralized control.

Distributed (Cascaded) Splitting

• Multiple splitters are deployed in series across the network.
• Structure: OLT → Splitter 1 → Splitter 2 → ONT
• Can include unbalanced splits or optical taps to adjust power along the route .
• Advantages: Reduces fiber count in long-distance deployments, allows flexible expansion, and can optimize network cost.
• Typically housed in closures or pedestals, with less flexibility for changing customer assignments.

Split Ratio Planning

• Common split ratios: 1×2, 1×4, 1×8, 1×16, 1×32, 1×64; odd ratios like 1×3 or 1×5 are occasionally used .
• The overall network split ratio is determined by the PON type (e.g., GPON, XGS-PON) and subscriber density.
• Higher split ratios reduce the number of OLT ports needed but increase insertion loss, which may limit reach or require higher-power OLTs .

Deployment Considerations

• Network Scalability: Adding new subscribers is easier with centralized splitters if capacity remains.
• Cost Efficiency: Splitters reduce the number of fibers and OLT ports required, lowering both CAPEX and OPEX .
• Performance: PLC splitters are preferred for large splits due to uniformity and lower insertion loss, while FBT splitters are suitable for small, cost-sensitive deployments .
• Maintenance: Centralized architectures simplify troubleshooting, while distributed architectures may require more field work.

Conclusion

An effective optical splitter network solution balances splitter type, split ratio, and architecture to optimize cost, scalability, and performance. Centralized splitting is ideal for manageable, high-flexibility networks, while distributed splitting supports long-distance or high-density deployments. Selecting the right combination of PLC or FBT splitters and planning split ratios carefully ensures reliable, efficient FTTH PON networks .