Fibre Optic Technician interview questions and answers

"A customer link is down. How do you find the fault?"

Work from the ends inward. Confirm the fault is in the fibre rather than the equipment: check the optical power at the receiver and whether the far end is transmitting. Inspect and clean the connectors at each patch panel, because contamination causes a large share of faults and costs nothing to rule out.

If the link is still down, test with an OTDR from one end to locate the event, then from the far end to confirm, since a break near the launch can hide behind the dead zone. Once located, plan the repair: expose the cable, splice, test again, and record the new route loss.

"How do you know a splice is good?"

Judge it on measurement, not appearance. The splicer estimates loss, but that estimate is not proof. A good splice shows a low, consistent loss on the OTDR from both directions, because a splice between fibres of slightly different characteristics can read low from one side and high from the other.

Mention the preparation that produces good splices: clean fibre, a square cleave, correct stripping, a maintained cleaver blade and a clean splicer. Most poor splices are decided before the arc fires.

"What does a spike in an OTDR trace mean?"

It is a reflection, typically from a connector, a mechanical splice or a break with a flat end face. A fusion splice normally shows as a small step with no reflection. Explain that the height of the step shows the loss and the position shows the distance, and that reflections matter because they can disturb transmitters as well as indicate a joint.

"How do you protect a cable during installation?"

Respect two limits: the maximum pulling tension and the minimum bend radius, both from the cable specification. Use lubricant and guides in ducts, pull with a swivel and a monitored tension, and never pull round a tight corner. Protect the ends against moisture, leave enough slack for future splices, and secure and label everything before leaving site.

"What safety rules do you follow when working with fibre?"

Never look into a fibre end or an active port, and use a power meter to confirm a fibre is dark rather than your eyes. Handle cleaved offcuts carefully, collecting them in a dedicated container, because they are almost invisible and get into skin. Then cover the ordinary site risks: working at height, confined spaces in manholes, traffic management on roadside work, and the permits that go with each.

"A splice loss is higher than the budget allows. What do you do?"

Re-splice rather than accept it. Before cutting, check the preparation: the cleave, the cleanliness, and whether the two fibres are the same type. Then re-splice and re-test. If it remains high after several attempts, suspect a mismatch between the fibres or damage further along, and test the section separately.

"Tell us about a difficult repair."

Describe a real one: the symptom, what you measured, how you narrowed the location, what the cause turned out to be, and how you proved the repair. Panels are listening for method and for care with records, because the next technician will rely on what you wrote down.