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IT Support & Hardware · Advanced

Link Loss Budget

The calculated maximum allowable optical loss for a fiber link based on fiber, connectors, and splices.

Definition

Loss budget sums fiber attenuation per kilometer plus loss per connector pair (often 0.75 dB maximum per TIA) and per splice (0.3 dB). Measured loss from an optical loss test set must be below the budget and within the transceiver's power budget.

Example

A 2 km single-mode link at 0.4 dB/km with two connector pairs: 0.8 + 1.5 = 2.3 dB budget.

Exam tip

Calculate loss budget before testing; measured loss above budget fails.

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