Multimode LC/LC Cable: Why SR SFP Beats LR and QSFP
Short answer
B Use an SR SFP transceiver because short-reach SR optics are built for multimode fiber and the SFP form factor provides the duplex LC connector that the LC/LC cable requires.
Question
Key Takeaways
This item tests whether you can separate reach (SR vs. LR) from form factor and connector (SFP vs. QSFP) and match both to a multimode LC/LC cable.
For a multimode LC/LC fiber cable, the correct transceiver is an SR SFP because SR optics are designed for short-reach multimode fiber and SFP modules use duplex LC connectors.
Common mistake: The likely wrong pick is A (LR SFP): it uses the same duplex LC connector, so it looks compatible, but LR is a long-reach single-mode optic and does not match the multimode cable.
Expert Analysis
The reach boundary: SR vs LR
The first decision is not the connector; it is the fiber type. An LC/LC cable is just a duplex connector pair, and both SR and LR optics can present LC ports. The SR (short reach) designation is the one tied to multimode fiber and short-wavelength optics, typically 850 nm, over building-scale distances. LR (long reach) is engineered for single-mode fiber and longer spans, typically 1310 nm. Putting an LR SFP on multimode cable crosses the media boundary the question is testing.
The form-factor boundary: SFP vs QSFP
The second trap is assuming LC means any LC-capable module. A standard SFP/SFP+ is a single-lane module with a duplex LC interface, which matches an LC/LC cable directly. QSFP/QSFP+ is a four-lane module; its common 40G SR4 optics use an MPO/MTP ribbon connector, not a duplex LC pair. Some QSFP variants can use LC, but that does not make QSFP the default or best fit for a simple multimode LC/LC link.
Applying both tests
Option B, the SR SFP, is on the correct side of both boundaries: short-reach multimode optics in an SFP package with a duplex LC port. Option A (LR SFP) has the right connector but the wrong reach/media design. Options C and D move to a QSFP form factor, which is unnecessary and usually mismatched to LC/LC multimode cabling. The supplied comment makes the same distinction: SR is short-wavelength and designed for MMF, while SFP natively provides a small duplex LC port. That is exactly why B is the answer.
Official Reference
https://www.comptia.org/certifications/network
This link opens the official vendor documentation in a new tab.
Exam Strategy
When a transceiver question names a fiber cable and connector, classify the cable first: multimode points to SR, single-mode points to LR. Then check the lane count and connector: a duplex LC/LC cable fits a single-lane SFP, while common QSFP SR4 optics expect MPO/MTP. Eliminate options that match only the connector but violate the fiber type.
Frequently Asked Questions
Why is an SR SFP the correct choice for a multimode LC/LC cable?
Can a QSFP transceiver be used with an LC/LC multimode cable instead of an SFP?
What is the main difference between SR and LR transceivers?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
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ERB14 👍 1 Answered BSR (Short Reach): Transceivers designated as SR use short-wavelength light and are designed specifically for multimode fiber (MMF) cables over shorter distances. SFP (Small Form-factor Pluggable): Standard SFP/SFP+ transceiver modules natively feature a small duplex LC connector port.
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