- A
Multimeter
Why wrong: A multimeter cannot measure optical power or loss in fiber optic cables.
- B
Tone generator
Why wrong: A tone generator works with copper cables, not fiber optics.
- C
OTDR
An OTDR is the standard tool for characterizing fiber optic links, measuring loss and locating faults.
- D
Wi-Fi analyzer
Why wrong: A Wi-Fi analyzer is for wireless networks and cannot test fiber optics.
Question 577 of 1,020
OTDR: Diagnose Fiber Optic Cable Loss and Faults
This 220-1201 practice question tests your understanding of networking tools. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network administrator is troubleshooting a slow connection between two buildings connected by a fiber optic link. The link is up but throughput is lower than expected. Which tool should be used to measure the exact signal loss in the fiber?
Quick Answer
The answer is an optical time-domain reflectometer (OTDR), which is the correct tool to measure exact signal loss in a fiber optic link. An OTDR works by sending a series of light pulses into the fiber and analyzing the backscatter and reflections that return, allowing it to pinpoint the location and severity of loss caused by splices, bends, or damage. On the CompTIA A+ Core 1 220-1201 exam, this question tests your ability to distinguish between tools used for fiber troubleshooting—a common trap is confusing the OTDR with a simple visual fault locator or power meter, which only measure total loss or find gross breaks, not the detailed profile needed for diagnosing throughput issues. Remember the memory tip: OTDR stands for “Optical Time-Domain Reflectometer,” and think of it as the “radar” for fiber—it sends out a pulse and listens for the echo to map every foot of the cable.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
OTDR
An Optical Time-Domain Reflectometer (OTDR) is the correct tool because it sends a series of optical pulses into the fiber and measures the backscattered and reflected light to calculate the exact signal loss (attenuation) at specific points along the link. This allows the administrator to identify splices, bends, or connectors causing excessive loss, which directly explains the low throughput despite the link being up.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Multimeter
Why it's wrong here
A multimeter cannot measure optical power or loss in fiber optic cables.
- ✗
Tone generator
Why it's wrong here
A tone generator works with copper cables, not fiber optics.
- ✓
OTDR
Why this is correct
An OTDR is the standard tool for characterizing fiber optic links, measuring loss and locating faults.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Wi-Fi analyzer
Why it's wrong here
A Wi-Fi analyzer is for wireless networks and cannot test fiber optics.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse a 'link being up' with 'no signal loss,' leading them to overlook the need for an OTDR and instead choose a multimeter or tone generator, which are irrelevant to fiber optics.
Detailed technical explanation
How to think about this question
An OTDR works by launching a high-power laser pulse and analyzing the Rayleigh backscatter and Fresnel reflections over time, converting time-of-flight into distance to pinpoint faults. A subtle behavior is that the OTDR's dead zone (the distance after the launch pulse where reflections saturate the receiver) can mask near-end connector loss, so a launch cable is often used to get accurate measurements at the first connector. In real-world scenarios, a dirty or damaged connector at the patch panel can cause 0.5–1 dB loss that accumulates across multiple links, reducing throughput without breaking the link.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Networking Tools — This question tests Networking Tools — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: OTDR — An Optical Time-Domain Reflectometer (OTDR) is the correct tool because it sends a series of optical pulses into the fiber and measures the backscattered and reflected light to calculate the exact signal loss (attenuation) at specific points along the link. This allows the administrator to identify splices, bends, or connectors causing excessive loss, which directly explains the low throughput despite the link being up.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on 220-1201
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting intermittent packet loss on a critical link between two buildings. The link uses single-mode fiber optic cable. Which tool is specifically designed to measure the length of the fiber and locate breaks or splices that could cause signal loss?
hard- A.Light meter
- ✓ B.OTDR
- C.Multimeter
- D.Cable tester
Why B: An Optical Time-Domain Reflectometer (OTDR) is the correct tool because it sends a series of light pulses into the fiber and measures the backscattered and reflected light to calculate fiber length, locate breaks, splices, and connectors, and quantify loss at each event. This makes it ideal for troubleshooting intermittent packet loss caused by physical impairments in a single-mode fiber link between buildings.
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Last reviewed: Jul 4, 2026
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