What is true about the QSFP-DD MPO-12 eDR4 transceiver?

Question

Options

• AThe maximum speed it can achieve is only 40 Gbps
• BThe maximum distance it can run is 71-100 meters
• CThe maximum speed it can achieve is 400 Gbps
• DIt only works with MMF fiber type

• B
  3% (1)
• C
  94% (34)
• D
  3% (1)

Explanation

Option C is correct because QSFP-DD (Quad Small Form-factor Pluggable Double Density) is specifically designed for 400 Gbps throughput, using 8 electrical lanes at 50 Gbps each - making it the industry-standard 400G form factor.

Why the distractors are wrong:

• A (40 Gbps): 40 Gbps belongs to the older QSFP+ form factor. QSFP-DD doubles the lane count of QSFP28, pushing it to 400G.
• B (71–100 meters): That range describes short-reach MMF transceivers (like SR4/SR8). The eDR4 variant uses single-mode fiber and can reach up to 500 meters (DR4) or beyond with extended reach.
• D (MMF only): eDR4 uses single-mode fiber (SMF), not multimode. MMF variants carry labels like SR8. The MPO-12 connector here carries 4 SMF TX/RX lane pairs.

Memory tip: Break down the acronym - QSFP-DD = "Double Density" = double the 200G QSFP28 → 400G. The "eDR4" suffix signals extended reach over single-mode, so think "e = extended, D = distance, SMF." If you see SR (short reach), think MMF; if you see DR/eDR/FR/LR, think SMF.

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