DCI Fiber Optic Installation 3 — Questions and Answers
Question 1: A fusion splice typically achieves what maximum average insertion loss?
- 0.5 dB
- 0.1 dB (Correct answer)
- 1.0 dB
- 0.3 dB
Correct answer: 0.1 dB
A well-executed fusion splice typically achieves 0.1 dB or less of insertion loss, far lower than mechanical splices.
Question 2: What is the purpose of optical fiber gel or index-matching gel in a mechanical splice?
- To lubricate the fiber for easier insertion
- To fill the air gap and reduce Fresnel reflection loss (Correct answer)
- To protect the splice from moisture
- To increase the fiber's numerical aperture
Correct answer: To fill the air gap and reduce Fresnel reflection loss
Index-matching gel has a refractive index close to glass, filling any gap between fiber ends to reduce Fresnel reflection and insertion loss.
Question 3: Which standard defines the insertion loss and return loss specifications for fiber optic connectors used in telecommunications?
- TIA-568-C.3 (Correct answer)
- ANSI/TIA-598
- IEC 60793
- IEEE 802.3
Correct answer: TIA-568-C.3
TIA-568-C.3 (now part of TIA-568.3-D) specifies optical fiber cabling components including connector insertion loss and return loss limits.
Question 4: What is the primary difference between OM3 and OM4 multimode fiber?
- OM4 supports single-mode transmission
- OM4 has a larger core diameter
- OM4 has higher bandwidth (EMB) supporting longer 10G/40G/100G distances (Correct answer)
- OM4 uses a different wavelength window
Correct answer: OM4 has higher bandwidth (EMB) supporting longer 10G/40G/100G distances
OM4 has a higher effective modal bandwidth (EMB) than OM3, extending 10G Ethernet to 550 m and 100G to 150 m versus OM3's shorter distances.
Question 5: When measuring fiber optic link loss with an optical loss test set (OLTS), what does a bidirectional test reveal that a single-direction test does not?
- Total fiber length
- Connector polish grade
- Asymmetrical loss from connectors or splices (Correct answer)
- Cable jacket type
Correct answer: Asymmetrical loss from connectors or splices
Bidirectional testing averages out directional loss differences at connectors, revealing asymmetrical problems that a one-way measurement would hide.
Question 6: What does 'macrobending loss' in fiber optics refer to?
- Loss caused by impurities in the fiber core
- Signal loss from large bends exceeding the minimum bend radius (Correct answer)
- Loss at connector interfaces
- Dispersion in long fiber runs
Correct answer: Signal loss from large bends exceeding the minimum bend radius
Macrobending loss occurs when fiber is bent beyond its minimum bend radius, causing light to radiate out of the core.
Question 7: Which fiber optic cable construction type uses individual 250 µm coated fibers laid in a gel-filled tube?
- Tight-buffered cable
- Loose-tube cable (Correct answer)
- Ribbon cable
- Breakout cable
Correct answer: Loose-tube cable
Loose-tube cables house individual 250 µm fibers in a gel-filled buffer tube, providing protection against moisture and temperature variation.
DCI Fiber Optic Installation 3
A fusion splice typically achieves what maximum average insertion loss?