What is the ferrule diameter for standard fibre optic connectors (LC, SC, ST)?

LC connectors use a 1.25mm ferrule (small form factor), while SC and ST connectors use 2.5mm ferrules. The smaller LC size enables higher port density.

What is the typical return loss specification for a UPC (Ultra Physical Contact) connector?

UPC connectors typically achieve >50 dB return loss (some specify >55 dB). The slightly domed end-face creates good physical contact, minimising reflections.

Why cannot APC (Angled Physical Contact) connectors be mated with UPC connectors?

APC connectors have an 8° angled end-face. When mated with flat UPC connectors, they make contact at only one point (or no contact), causing extremely high loss and potential damage.

The 8° angle prevents proper end-face contact, causing high loss

The ferrule diameters differ, so they cannot be inserted

UPC uses singlemode fibre while APC uses multimode

The keying features are incompatible between the two types

Free mock exam

Connectors and Splicing — Fibre Optics Practice

Free topic-focused mock exam: 30 random questions from a pool of 42 on Connectors and Splicing, 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: 42

Free, no sign-up. Retake as many times as you like — different questions each time.

Sample questions

01What is the ferrule diameter for standard fibre optic connectors (LC, SC, ST)?
- A2.5mm for all types
- B1.25mm for all types
- C3.0mm for SC, 2.5mm for LC/ST
- D1.25mm for LC, 2.5mm for SC/ST
Why: LC connectors use a 1.25mm ferrule (small form factor), while SC and ST connectors use 2.5mm ferrules. The smaller LC size enables higher port density.
02What is the typical return loss specification for a UPC (Ultra Physical Contact) connector?
- A>70 dB
- B>20 dB
- C>30 dB
- D>50 dB
Why: UPC connectors typically achieve >50 dB return loss (some specify >55 dB). The slightly domed end-face creates good physical contact, minimising reflections.
03Why cannot APC (Angled Physical Contact) connectors be mated with UPC connectors?
- AThe ferrule diameters differ, so they cannot be inserted
- BUPC uses singlemode fibre while APC uses multimode
- CThe 8° angle prevents proper end-face contact, causing high loss
- DThe keying features are incompatible between the two types
Why: APC connectors have an 8° angled end-face. When mated with flat UPC connectors, they make contact at only one point (or no contact), causing extremely high loss and potential damage.

Common questions

Is the Connectors and Splicing 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.