Split ratio of the optical splitter

The splitting ratio of an optical splitter defines how the input optical power is divided among its output ports, commonly expressed as 1:N or 2:N, where N is the number of outputs.

Definition and Purpose

The splitting ratio indicates the distribution of optical power from a single input fiber to multiple output fibers. For example, a 1:8 splitter divides the input signal equally among eight outputs, with each receiving 1/8th of the total power, while a 50:50 splitter evenly splits power between two outputs . This ratio is crucial in Passive Optical Networks (PONs) to ensure each subscriber receives adequate signal strength without overloading the optical line terminal (OLT) .

Common Split Ratios

• 1:N Splitters: One input port, N output ports (e.g., 1:2, 1:4, 1:8, 1:16, 1:32, 1:64). Widely used in star-topology PONs .
• 2:N Splitters: Two input ports, N output ports (e.g., 2:32, 2:64). Used in ring-topology PONs for redundancy, allowing one input to take over if the other fails .
• Non-uniform Splitters: Custom splitters with unequal power distribution, typically for specialized applications, but more expensive .

Splitter Types

• FBT (Fused Biconical Taper) Splitters: Cost-effective, suitable for small splits like 1:2 or 1:4 .
• PLC (Planar Lightwave Circuit) Splitters: High precision, uniform output, ideal for large splits like 1:32, 1:64, and stable across temperature variations .

Deployment Architectures

• Centralized Splitting: A single large splitter (e.g., 1×32 or 1×64) located at the central office or head-end. Pros include simpler maintenance and fewer field splices; cons include higher fiber count from the central office .
• Cascaded Splitting: Multiple smaller splitters in series (e.g., 1×4 followed by 1×16 to achieve 1×64). Pros include fewer feeder fibers and better coverage for wide or less dense areas .

Practical Considerations

• Optical Budget: Each split introduces insertion loss; higher split ratios reduce power per output, affecting signal margin .
• Distance and Reach: Longer fiber runs combined with high split ratios may require careful planning to maintain signal quality .
• Subscriber Demand: High-bandwidth users may require lower split ratios to ensure sufficient optical power .
• Cost Efficiency: Higher split ratios reduce the number of OLT ports needed, lowering infrastructure costs, but must balance with quality of service . In practice, 1:32 and 1:64 split ratios are common in FTTH deployments, balancing cost, performance, and scalability. Ultra-dense or short-loop networks may use higher ratios like 1:128 if the optical margin allows .