Free mock exam
Fibre basics and safety — Fibre Optics Practice
Free topic-focused mock exam: all 30 questions on Fibre basics and safety, drawn from the wider Fibre Optics bank. 35-minute timer, 70% to pass, worked explanation on every question. Use this when you've taken the full mock once and want to drill the topics you got wrong.
- Questions
- 30
- Time limit
- 35 min
- Pass mark
- 70% · 21/30
- Question bank
- 30
Free, no sign-up. Retake as many times as you like — the questions are reshuffled, with the answer order changed.
Sample questions
01While you strip a fibre for splicing, an apprentice asks whether the cladding comes off with the coating. What is the right answer?
- ANo, it is removed afterwards by the cleaver blade
- BNo, the cladding is glass and stays on the fibre
- CYes, but only on singlemode fibre with a 9 µm core
- DYes, the cladding is plastic and strips with the coating
Why: The core and cladding are one piece of glass, and the cladding is what traps the light in the core, so it cannot be stripped off. What you strip is the plastic coating and any buffer over it. Calling the cladding plastic is the tempting mistake, because it sits under the coating, but it is glass on singlemode and multimode alike. The cleaver cuts the glass across; it does not remove a layer.
02Bare glass fibre measures 125 µm across the cladding. On most fibre, how wide is it once the primary coating is on?
- AAbout 900 µm
- BAbout 62.5 µm
- CAbout 125 µm
- DAbout 250 µm
Why: The primary coating on most fibre is 250 µm across. 900 µm is tempting because it is the other figure you meet on indoor cables and pigtails, but that is a tight buffer added over the 250 µm coating. 62.5 µm is a multimode core size, inside the cladding, and 125 µm is the bare glass before any coating goes on.
03A fibre data sheet quotes a numerical aperture. What does that figure describe?
- AThe loss of the fibre per kilometre at 850 nm
- BThe modal bandwidth of the fibre per km
- CThe diameter of the core, in micrometres
- DThe range of angles the fibre will accept
Why: Numerical aperture sets the range of angles at which light entering the fibre is accepted and kept in the core by total internal reflection. You do not need to calculate it. Core diameter is tempting because it is also on the data sheet, but it is quoted as a size such as 50/125. Loss and bandwidth are separate figures.
Common questions
Is the Fibre basics and safety mock exam free?
Yes — 100% free, no sign-up needed. Questions are pulled at random from a substantial bank, with a worked explanation on every question after you submit.
Can I retake the mock exam?
Yes. Every attempt picks a different random selection and reshuffles the options, so each retake gives you genuinely new questions. No limit on retakes.
Does this count towards the real qualification?
No — this is independent practice material. To gain the actual qualification you need to sit the official assessment through an approved provider.