CFOT Fiber Optic Cleaning and Inspection 2 — Questions and Answers
Question 1: How many inspection zones are defined for single-mode connector end-faces per IEC 61300-3-35?
- 2
- 3
- 4 (Correct answer)
- 5
Correct answer: 4
IEC 61300-3-35 defines four concentric zones (A, B, C, D) from the core outward to the contact area of the connector end-face.
Question 2: What purity level of isopropyl alcohol (IPA) is recommended for cleaning fiber optic connectors?
- 70%
- 91%
- 99% (Correct answer)
- 50%
Correct answer: 99%
99% pure IPA minimizes water residue that could contaminate the end-face or cause spotting after the solvent evaporates.
Question 3: Which cleaning tool is designed specifically to clean the ferrule end-face of a connector installed inside an adapter?
- Reel-type cassette cleaner
- Stick cleaner (push-to-clean device) (Correct answer)
- Lint-free wipe pad
- Pressurized air canister
Correct answer: Stick cleaner (push-to-clean device)
Stick cleaners are inserted into adapters to contact and clean the ferrule end-face without removing the connector from the bulkhead.
Question 4: What contaminant transferred by direct hand contact with fiber end-faces is particularly problematic because it leaves a persistent film?
- Metallic dust from cutting tools
- Skin oils (Correct answer)
- Moisture condensation
- Cladding buffer material
Correct answer: Skin oils
Skin oils form a thin, persistent film that bonds strongly to the glass surface and significantly increases insertion loss if not properly cleaned.
Question 5: Per IEC 61300-3-35, what is the allowable number of scratches in Zone A (core region) for a single-mode PC connector to pass inspection?
- Up to 3 scratches ≤3 μm wide
- No scratches are allowed in Zone A (Correct answer)
- Up to 1 scratch ≤5 μm wide
- Up to 5 scratches of any size
Correct answer: No scratches are allowed in Zone A
Zone A of a single-mode PC connector must be completely free of scratches to meet IEC 61300-3-35 pass criteria because any scratch directly blocks the light path.
Question 6: How should fiber optic connectors be stored when they are not mated or in use?
- Leave them exposed to monitor for environmental damage
- Cap them with protective dust caps (Correct answer)
- Wrap them in standard paper towels
- Submerge them in an IPA solution
Correct answer: Cap them with protective dust caps
Dust caps protect the ferrule end-face from airborne contamination and physical damage when connectors are not mated.
Question 7: What can occur when two contaminated fiber end-faces are mated under the spring pressure of a connector?
- Contamination is destroyed by the compression force
- Hard particles can be embedded into the glass causing permanent damage (Correct answer)
- Signal loss temporarily increases then self-corrects over time
- Contamination migrates only to the outer contact zone
Correct answer: Hard particles can be embedded into the glass causing permanent damage
The mating force can embed hard particles into the polished glass surface, causing permanent pits or scratches that cannot be removed by any cleaning method.
CFOT Fiber Optic Cleaning and Inspection 2
How many inspection zones are defined for single-mode connector end-faces per IEC 61300-3-35?