How to determine the quota for fused optical cable

The quota for fused optical cable is determined by calculating the loss budget, which sums the expected losses from fiber, fusion splices, connectors, and any passive components to ensure the system meets performance requirements.

Understanding Loss Budget

A loss budget (or attenuation allowance) is the total allowable optical loss in a fiber optic link. It is calculated by summing the expected losses from all components in the cable plant, including: Fiber attenuation: Typically 0. 1 dB per 100 feet (30 m) for multimode at 850 nm, or 0.

1 dB per 300 feet (100 m) at 1300 nm, and lower for singlemode fibers. Fusion splices: Standard singlemode fusion splices usually have a loss of about 0. 15 dB per splice.

Connectors: Most adhesive/polish or fusion splice-on connectors have a loss of 0. 3 dB, while prepolished/mechanical or multifiber connectors like MPOs can have up to 0. 75 dB per connector.

Passive components: Splitters or other devices in PON networks add additional loss, which should be included in the budget. The loss budget is then compared to the measured insertion loss using a light source and power meter or OTDR to verify that the cable plant is within acceptable limits.

Calculating Quota for Splice Closures

The quota for a fiber optic splice closure refers to the number of fibers or splices it can accommodate while maintaining the loss budget. Key considerations include: Closure capacity: Each splice tray has a maximum number of fusion splices it can hold. For example, a closure may support 24, 48, or 96 fibers depending on the design.

Cable type and core count: Aluminum or copper core cables, single-core or multi-core, affect the material and labor factors when calculating installation quotas. Multiplication factors: Labor, material, and mechanical factors are applied based on cable type and core count to determine the effective quota for installation planning.

Practical Steps

List all components in the fiber link: fiber length, number of splices, connectors, and passive devices. Assign standard loss values to each component (e.g., 0. 15 dB per fusion splice, 0.

3 dB per connector). Sum the losses to calculate the total expected loss. Compare with system power budget: Ensure the total loss does not exceed the transmitter-receiver power margin.

Adjust closure quota: Based on the number of fibers and splices, ensure the closure can accommodate all splices without exceeding the loss budget. Tools and ReferencesFOA provides an online Loss Budget Calculator and a mobile app to simplify these calculations. Standards such as EIA/TIA-568 provide maximum allowable losses for connectors and splices, which should be referenced when determining quotas.

By following these steps, you can determine the quota for fused optical cable in terms of both physical capacity and optical performance, ensuring reliable network operation.