Cisco QSFP-40G-SR-BD — 40G bidirectional QSFP+ over duplex LC (no MPO), up to 150 m

What it is: A 40-Gbps QSFP+ optical transceiver that runs 40GBASE-SR-BiDi over two wavelengths on one duplex LC multimode fiber. It lets you turn existing duplex MMF (OM3/OM4) links into 40G without pulling MPO trunks—perfect for quick 10G→40G upgrades.

Why buyers pick QSFP-40G-SR-BD (plain English)

• No MPO needed: uses your existing LC duplex patching—huge cost/time saver during upgrades.

• Fast migrations: drop-in 40G on older 10G fiber runs (within BiDi distances).

• Simple ops: standard QSFP+ slot, familiar DOM/diagnostics, and standard LC jumpers.

60-second spec box

Optics & reach

• Fiber / connector: MMF, duplex LC

• Distances: up to 100 m on OM3 • up to 150 m on OM4

Wavelengths / modulation

• Bidirectional WDM: two wavelengths carried in each fiber strand (one up, one down); typical λ around ~850 nm / ~910 nm (approximate)

Line rate & interface

• 40G Ethernet (4×10G internal lanes, presented as 40G)

• QSFP+ form factor with digital diagnostics (DOM)

Compatibility notes

• Point-to-point 40G only over LC MMF

• Does not support 4×10G breakout fan-out (use QSFP-40G-SR4 for breakout)

Electrical / power

• 3.3 V supply • ~3.0–3.5 W max power draw (typical QSFP+ SR-BiDi class)

Environment

• Operating temp: 0 to +70 °C (commercial)

• Hot-pluggable QSFP+

Where it fits (and when to choose something else)

• Perfect for: top-of-rack ↔ aggregation and closet-to-MDF links where you already have LC duplex MMF and need 40G up to 100 m (OM3) / 150 m (OM4).

• Choose QSFP-40G-SR4 (MPO-12) if you want 4×10G breakout or have MPO plant.

• Choose LR4 (single-mode, LC) for 10 km reach, or ER4/ZR for even longer.

Quick design tips (no-regret)

• Use BiDi at both ends: both sides must be QSFP-40G-SR-BD—it won’t interop with SR4 on the far end.

• Verify fiber type & length: check your installed MMF grade (OM3 vs OM4) and patch count to stay inside the distance budget.

• Clean those LCs: short-reach, high-speed optics are very sensitive to dirty connectors—clean before testing.

• Polarity A↔B: standard duplex LC polarity; avoid flipped jumpers in the middle of the link.

TL;DR

QSFP-40G-SR-BD = 40G over duplex LC MMF (no MPO), 100 m on OM3 / 150 m on OM4, QSFP+ with DOM. It’s the fastest, least-disruptive way to light up 40G on your existing duplex fiber plant.