Question 446 of 520

Network Implementation →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is attenuation due to distance, as multimode fiber is inherently limited in range compared to single-mode fiber. This occurs because modal dispersion and higher absorption rates cause the optical signal to weaken significantly over long spans, and at 2 km the loss exceeds the link’s power budget, resulting in a weak signal at the receiver. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of fiber types and their distance limitations—a common trap is confusing attenuation with dispersion or assuming all fiber can handle long hauls. Remember that multimode fiber is designed for shorter runs, typically under 550 meters for high speeds, while single-mode fiber is built for distances beyond 2 km. A useful memory tip: “Multi for short, Single for long” helps you quickly match the fiber type to the required distance.

N10-009 Network Implementation Practice Question

This N10-009 practice question tests your understanding of network implementation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 company has just installed a new fiber optic connection between two buildings 2 km apart. The connection is using multimode fiber. However, the signal is too weak at the receiving end. What is the most likely cause?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1mediummultiple choice

Full question →

A
Attenuation due to distance
Multimode fiber has a maximum effective distance that varies by speed but is generally under 1 km for higher data rates. 2 km exceeds that limit, causing significant signal loss (attenuation).
B
Electromagnetic interference
Why wrong: Fiber optic cables are immune to electromagnetic interference because they transmit light, not electrical signals. EMI would not cause signal weakening in fiber.
C
Incorrect termination
Why wrong: While incorrect termination can cause light loss, the most likely issue over such a long distance is distance-related attenuation. Termination issues are more likely to cause total failure or high loss at the connection points, not gradual weakening along the run.
D
Crosstalk
Why wrong: Crosstalk occurs in copper cables when signals interfere with each other. Fiber optics do not experience crosstalk in the same way.

Full breakdown with real-world context →

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

✓

Attenuation due to distance

Multimode fiber (MMF) is designed for shorter distances, typically up to 550 meters for 10 Gbps (OM3/OM4) and up to 2 km only for lower speeds like 100 Mbps or 1 Gbps using older OM1/OM2 fiber. At 2 km, the signal attenuation exceeds the power budget of the MMF link, causing a weak signal at the receiver. Single-mode fiber (SMF) would be required for reliable transmission over this distance.

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.

✓
Attenuation due to distance
Why this is correct
Multimode fiber has a maximum effective distance that varies by speed but is generally under 1 km for higher data rates. 2 km exceeds that limit, causing significant signal loss (attenuation).
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Electromagnetic interference
Why it's wrong here
Fiber optic cables are immune to electromagnetic interference because they transmit light, not electrical signals. EMI would not cause signal weakening in fiber.
✗
Incorrect termination
Why it's wrong here
While incorrect termination can cause light loss, the most likely issue over such a long distance is distance-related attenuation. Termination issues are more likely to cause total failure or high loss at the connection points, not gradual weakening along the run.
✗
Crosstalk
Why it's wrong here
Crosstalk occurs in copper cables when signals interfere with each other. Fiber optics do not experience crosstalk in the same way.

Common exam traps

Common exam trap: answer the scenario, not the keyword

CompTIA often tests the misconception that fiber is immune to all distance limitations, but the trap here is that multimode fiber has strict distance limits due to modal dispersion and higher attenuation, unlike single-mode fiber which can span 2 km easily.

Detailed technical explanation

How to think about this question

Fiber optic attenuation is measured in dB/km and varies by wavelength (e.g., 3.5 dB/km at 850 nm for MMF vs. 0.4 dB/km at 1310 nm for SMF). The power budget calculation must account for connector losses (0.5–1 dB per pair) and splice losses; exceeding the budget results in a receiver signal below the minimum threshold, causing bit errors or link failure. In practice, a 2 km MMF link at 1 Gbps over OM1 fiber would have a total loss of ~7 dB (2 km × 3.5 dB/km), which may still work with high-power optics, but at 10 Gbps the distance limit is much shorter (e.g., 300 m for OM3).

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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.

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 N10-009 question test?

Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Attenuation due to distance — Multimode fiber (MMF) is designed for shorter distances, typically up to 550 meters for 10 Gbps (OM3/OM4) and up to 2 km only for lower speeds like 100 Mbps or 1 Gbps using older OM1/OM2 fiber. At 2 km, the signal attenuation exceeds the power budget of the MMF link, causing a weak signal at the receiver. Single-mode fiber (SMF) would be required for reliable transmission over this distance.

What should I do if I get this N10-009 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 30, 2026

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This N10-009 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the N10-009 exam.