SFP+ vs SFP28: How Should I Choose?

I see teams stuck between 10G and 25G. Projects slip while people debate specs, cost, and timelines. The risk is buying the wrong speed and living with it for years. I break the choice into distance, density, power, and roadmap so you can move.

Pick SFP+ when your links are ≤10G, distances are short-to-medium, budgets are tight, or older switches dominate. Pick SFP28 when you need 25G per lane, higher rack density, lower watts per G, or a clean upgrade path to 100/200/400G. Match optics to fiber type and vendor lists.

I am Candy from ABPTEL in Shenzhen. I run B2B builds with operators and data centers. I have seen 10G serve well for years, and I have seen 25G erase bottlenecks in one weekend. Below is how I frame the decision with engineers, buyers, and PMs before we lock POs.

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What is SFP+, and when is it still the right call?

SFP+ is the 10G workhorse. It is the small form-factor successor to early 10G modules. It follows the SFF-8431¹ electrical spec and supports 10 Gigabit Ethernet², 8G Fibre Channel, and OTU2. It is compact, cost-effective, and everywhere in access, aggregation, and server NICs.

Use SFP+ when links stay at 10G, fiber is already in place, and your switches are 10G-centric. It has broad vendor support, low price, and many SKUs (SR, LR, ER, ZR, BiDi, CWDM/DWDM, DAC, AOC). It is smaller than older XENPAK/XFP³ and remains the dominant 10G option.

Common SFP+ link types

Link type	Fiber/Copper	Typical reach	Notes
10GBASE-SR (SFP+ SR4)	MMF OM3/OM4	300–400 m	Low cost in-building
10GBASE-LR (SFP+ LR)	SMF	10 km	Metro/access staple
10G DAC (Twinax)	Copper	1–7 m	TOR to server, very low power
10G AOC	Active fiber	3–30 m+	Clean cabling, EMI immune

Where SFP+ still wins

• Broad second-hand and spare stock.
• Simple monitoring and automation; many teams know it well.
• Lowest cost per port when the demand is 10G.

SFP+ pitfalls to watch

• Hidden oversubscription at leaf-spine when east-west traffic grows.
• Fan and power rise if you scale port count instead of speed.
• Future 25G/100G migrations may require new line cards or switches.

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What is SFP28, and when do I need 25G?

SFP28 keeps the same compact shell as SFP+, but each lane runs at 25G. It is the standard optic for 25 Gigabit Ethernet⁵ server NICs and 32G Fibre Channel. It pairs well with 100G leaf-spine because four lanes of 25G aggregate cleanly to 100G uplinks via CAUI-4 lane mapping⁶.

Choose SFP28 when servers push >10G, storage needs 25G, or you plan a 100G spine. It offers higher port density, lower watts per G, and better long-term cost than stacking more 10G. It supports SR, LR, BiDi, CWDM, DAC, and AOC with broad vendor adoption.

SFP28 portfolio at a glance

Link type	Fiber/Copper	Typical reach	FEC/Notes
25GBASE-SR (SFP28 SR)	MMF OM3/OM4/OM5	70–150 m	Check host FEC7 on long MMF
25GBASE-LR (SFP28 LR)	SMF	10 km	Common in leaf-aggregation
25G DAC (SFP28)	Copper	1–5 m	Very low latency and power
25G AOC	Active fiber	3–30 m+	Clean pathways in dense racks

Why 25G scales better

• 25G per lane maps to 100/200/400G fabrics.
• Fewer ports to cable for the same throughput.
• Watts/Gbps often drops 30–50% vs 10G at scale.

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Can I mix SFP+ and SFP28 in the same switches and links?

Many teams want to drop 10G servers into a new 25G leaf, or run 25G in racks while core stays at 10G. The cage and latch look the same, but there are speed, FEC, and vendor list details that decide if it works cleanly.

A 25G port can often accept an SFP+ module and run at 10G; the reverse is not supported. Always confirm SFP28 backward compatibility⁸ and DAC/AOC EEPROM rules in the switch vendor list.

Compatibility matrix (typical behavior)

Host port	Plugged module	Expected result	Caveats
25G SFP28 port	SFP+ 10G optic/DAC	Runs at 10G	Set speed; vendor whitelist
10G SFP+ port	SFP28 25G optic/DAC	Not supported	Port cannot clock 25G
25G SFP28 port	SFP28 25G optic	Runs at 25G	FEC may be required
25G SFP28 port	AOC/DAC mix	Varies	Check cable code/length caps

Practical mixing tips

• Lock port speed explicitly when downshifting to 10G.
• Keep FEC settings aligned across both ends.
• Use vendor-approved part numbers for optics and DAC/AOC.
• Test BiDi and CWDM parts in a pilot rack before rollout.

Field note

I once merged a 10G SFP+ rack into a new 25G leaf for a finance client. We down-sped the ports, pinned FEC off, and used approved 10G DACs. Cutover finished in one night, then we upgraded rows to 25G over the next quarter with zero rewiring.

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Which one fits my distance, cabling, power, and budget needs?

The best choice matches link length, media you have, watts, and how fast the team must scale. A short copper run in a TOR rack is not the same as a building riser. A campus aggregation is not the same as a spine.

If most links are ≤3 m, DAC vs AOC⁹ tradeoffs matter: pick 10G SFP+ DAC or 25G SFP28 DAC by speed need. For 50–150 m inside buildings, MMF SR works; go 25G if you plan for growth. For ≥1 km, pick LR on SMF; favor 25G where you see traffic growth and spine upgrades.

Distance and media selector

Scenario	Media you have	SFP+ option	SFP28 option	My note
TOR to server ≤3 m	No fiber	10G DAC	25G DAC	Lowest cost/latency
TOR to server 3–20 m	No fiber	10G AOC	25G AOC	Clean cable mgmt
In-row 50–150 m	OM3/OM4	10G SR	25G SR	Check FEC on 25G SR
Riser/campus 1–10 km	SMF	10G LR	25G LR	Budget for spares
Leaf–Spine 100–300 m	OM4/OM5	10G SR (rare)	25G SR	25G aligns to 100G uplinks

Power and thermal (typical)

Module type	Typical power	Note
SFP+ SR/LR	~0.6–1.0 W	Lowest heat at 10G
SFP28 SR/LR	~1.0–1.5 W	More G per watt
10G DAC	~0.1–0.3 W	Host-only power
25G DAC	~0.2–0.5 W	Slightly higher, still low

Budget and lifecycle

Factor	SFP+ (10G)	SFP28 (25G)
Module unit price	Lower	Higher per unit, lower per G
Switch/line card cost	Lower	Higher, but fewer ports needed
Cabling density	Lower	Higher density per RU
3-year TCO at scale	Can rise with port count	Often lower per Gbps

Quick chooser (by role)

Role	Ask yourself	Likely pick
Procurement	Is budget tight and demand stable at 10G?	SFP+
Network PM	Do I need headroom without rewiring later?	SFP28
Engineer	Will 100G/400G uplinks land this year?	SFP28
Ops	Do we have large 10G installed base and spares?	SFP+ (now), plan SFP28 pilot

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Conclusion

The safe choice is not one speed for all. If traffic is steady and 10G fits, SFP+ saves money right now. If growth is real, SFP28 avoids a second build and maps cleanly to 100G fabrics. I advise teams to inventory media, model power, check vendor lists, and pilot both in one rack before they buy at scale. When you are ready, I can help validate optics (SR/LR/BiDi), DAC/AOC lengths, and switch compatibility for your exact BOM.