Fibre Optic Technician practice questions with answers

Updated 16 September 2026 · 2 min read

These questions concentrate on fibre optics and cabling, with networking alongside, because a fibre technician has to understand what the link carries as well as the glass itself. Answer each one as though you were standing at a splice closure with a customer waiting, then open the explanation and check your reasoning, not only your letter.

How this guide was made

Written for this site with AI assistance, then checked automatically before publishing. The topic table, sample questions, worked examples and study plan are generated from this site’s question bank: each worked example is recalculated by separate code, and each sample answer says where it came from.

The guide deliberately states no salaries, grades, pass marks or exam dates. Those change, and they could not be checked here, so take them from the advert itself.

This site is independent and is not affiliated with MIFOTRA or any employer.

Practice questions

You are terminating a 12-strand distribution cable. According to the standard TIA-598 color code, what is the color of fiber #6?
1. Red
2. Blue
3. White
4. Slate
Show the answer
C. White
The TIA-598 color code is: 1-Blue, 2-Orange, 3-Green, 4-Brown, 5-Slate, 6-White, 7-Red, 8-Black, 9-Yellow, 10-Violet, 11-Rose, 12-Aqua.
Original practice question, written against published exam objectives. Open this question
A technician spliced two pigtails in a splice tray. The link passes the initial OTDR test. Two days later, the link drops. When the tech opens the tray, the link suddenly comes back up. What is the likely issue?
1. The fusion splice was "cold" and needed exposure to air to heal
2. Light from the room illuminated the fiber and restored the signal
3. The pigtail jacket absorbed moisture from the air
4. The fiber was twisted or pinched by the splice tray lid, creating a macrobend under pressure
Show the answer
D. The fiber was twisted or pinched by the splice tray lid, creating a macrobend under pressure
Improper routing in a splice tray can cause the lid to pinch a fiber, inducing a severe macrobend or mechanical stress. Opening the tray relieves the pressure.
Original practice question, written against published exam objectives. Open this question
A data center needs to upgrade a 100-meter server-to-switch link to 40GBASE-SR4. What type of fiber and wavelength should they select for the most cost-effective solution?
1. OM1 multimode fiber operating at 1550nm
2. OS2 single-mode fiber operating at 1310nm
3. OM4 multimode fiber operating at 850nm
4. OS1 single-mode fiber operating at 1625nm
Show the answer
C. OM4 multimode fiber operating at 850nm
For short data center runs (up to 150m) at 40Gbps or 100Gbps, OM4 multimode fiber using VCSEL lasers at 850nm is the standard, cost-effective choice (SR4).
Original practice question, written against published exam objectives. Open this question
While analyzing an OTDR trace of a newly installed 5km single-mode link, you see a sharp spike upwards followed by a drop in the trace level. What physical event does this signature represent?
1. A non-reflective event, such as a perfect fusion splice
2. A reflective event with loss, such as a mechanical splice or connector
3. A ghost reflection from the launch cable
4. A macrobend in the fiber
Show the answer
B. A reflective event with loss, such as a mechanical splice or connector
A sharp spike indicates reflectance (Fresnel reflection), and the subsequent drop indicates insertion loss. This is the classic signature of a mated connector pair or mechanical splice.
Original practice question, written against published exam objectives. Open this question
You are shooting an OTDR trace on a short 100m patch cord but cannot see the connector at the far end clearly due to the initial pulse width. What setting should you adjust?
1. Change the wavelength from 1310nm to 1550nm
2. Increase the pulse width to push more power into the fiber
3. Decrease the pulse width to improve spatial resolution
4. Increase the averaging time to 3 minutes
Show the answer
C. Decrease the pulse width to improve spatial resolution
A shorter pulse width provides better spatial resolution, allowing the OTDR to distinguish closely spaced events, which is essential for short links.
Original practice question, written against published exam objectives. Open this question
What is the purpose of DNS?
1. To encrypt data
2. To store website data
3. To assign IP addresses
4. To translate domain names to IP addresses
Show the answer
D. To translate domain names to IP addresses
DNS resolves human-readable names to IP addresses. Assigning addresses is DHCP's job - a very common confusion.
Real past-paper question; answer cross-checked against the original session. Open this question
A small office connects all their computers to a single central switch. What physical topology is in use?
1. Bus
2. Mesh
3. Ring
4. Star
Show the answer
D. Star
Objective 1.2: A central switch with radiating connections forms a physical star topology. Ring uses sequential tokens, Mesh connects all, Bus uses a single backbone.
Original practice question, written against published exam objectives. Open this question
A vibration analyst reviews an FFT spectrum on a large centrifugal fan running at 1800 RPM (30 Hz). There is a massive spike exactly at 1X running speed (30 Hz). What is the most likely mechanical fault?
1. Mass unbalance of the fan rotor
2. Bearing inner race defect
3. Gear mesh failure
4. Cavitation
Show the answer
A. Mass unbalance of the fan rotor
A high vibration amplitude exactly at 1X turning speed is the classic signature of mass unbalance. The heavy spot causes one vibration peak per revolution.
Original practice question, written against published exam objectives. Open this question

Think in terms of the link

For any fault question, picture the whole path: transmitter, connector, fibre, splices, patch panel, connector, receiver. Then ask where the described symptom could come from. High loss on one fibre of a twelve-fibre cable points at a joint or an end face, while high loss on all of them points at the cable, the route or the equipment.

Keep a record of what caught you

Note every wrong answer by category: fibre types, splicing, connectors, test instruments, loss budgets or safety. Fibre knowledge is narrow enough that two or three weeks of this will show you exactly which area needs the work.

After this set

The worked calculations below cover loss budgets and decibel conversions, generated for this page and independently recomputed before publication. More fibre and networking questions from the full bank follow them.

Two calculations to try

Try each one on paper first. Every figure is generated and then recalculated by separate code before it is published.

Will this fibre link work?
A 18.5 km single-mode link runs at 1310 nm. Assume 0.35 dB/km fibre attenuation, 2 connectors at 0.5 dB each and 7 splices at 0.1 dB each. The transmitter launches 2 dBm and the receiver needs at least -24 dBm. What is the total link loss and the remaining margin?
Show the working
1. Fibre loss: 18.5 km × 0.35 dB/km = 6.47 dB
2. Connectors: 2 × 0.5 = 1 dB; splices: 7 × 0.1 = 0.7 dB
3. Total loss = 6.47 + 1 + 0.7 = 8.17 dB
4. Power budget = 2 − (-24) = 26 dB
5. Margin = 26 − 8.17 = 17.83 dB, comfortably above the 3 dB many designers keep in reserve for ageing and repairs.
Answer: Loss 8.17 dB, margin 17.83 dB
Converting milliwatts to dBm
A signal measures 1000 mW. Express it in dBm.
Show the working
1. dBm = 10 × log₁₀(P in mW).
2. dBm = 10 × log₁₀(1000) = 10 × 3
3. dBm = 30 dBm
Answer: 30 dBm

More from the full bank

Anyone can read these questions. Their answers and explanations open with an access code.

Common questions

Why do networking questions appear in a fibre set?

Fibre exists to carry a network. Technicians are regularly asked what a link is for, how it connects to switches or an optical line terminal, and whether a fault is in the fibre or the equipment.

How can I practise without a splicer?

Work the calculations, learn traces from published examples, and study connector inspection images. Ask your employer or training centre for supervised time with the instruments, because that part cannot be learned on paper.