RCDD · Question #153
What is the worst case acceptance value for attenuation when testing 2000 m (6562 ft) of 50/125 multimode fiber at a wavelength of 1300 nm when the fiber has 2 connector pairs and 3 splices?
The correct answer is C. 5.4 dB. Calculate worst-case fiber link attenuation by applying TIA-568 loss budgets for fiber, connector pairs, and splices using standard worst-case values.
Question
What is the worst case acceptance value for attenuation when testing 2000 m (6562 ft) of 50/125 multimode fiber at a wavelength of 1300 nm when the fiber has 2 connector pairs and 3 splices?
Options
- A3.4 dB
- B4.65 dB
- C5.4 dB
- D6.4 dB
- E9.4 dB
How the community answered
(40 responses)- B13% (5)
- C78% (31)
- D3% (1)
- E8% (3)
Why each option
Calculate worst-case fiber link attenuation by applying TIA-568 loss budgets for fiber, connector pairs, and splices using standard worst-case values.
3.4 dB is too low and cannot be derived from TIA-568 worst-case values for the given fiber length, connector pairs, and splices.
4.65 dB results from using an incorrect fiber attenuation rate or miscounting the number of connector or splice contributions.
Per TIA-568, 50/125 multimode fiber at 1300 nm has a maximum attenuation of 1.5 dB/km, so 2 km yields 3.0 dB. Adding 2 connector pairs at 0.75 dB each (1.5 dB total) and 3 splices at 0.3 dB each (0.9 dB total) produces a worst-case total of 5.4 dB, which matches the TIA-568 optical loss budget formula exactly.
6.4 dB overestimates the total loss and does not correspond to any valid TIA-568 worst-case calculation with these parameters.
9.4 dB far exceeds the TIA-568 worst-case budget and would require per-component loss values significantly higher than the standard specifies.
Concept tested: Fiber optic link loss budget calculation TIA-568
Source: https://www.thefoa.org/tech/ref/testing/test/loss.html
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