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SFP28 Optics in Data Centers

25G SFP28 optics are the standard optical transceivers used to connect 25 GbE Ethernet links in modern data centers. They are widely deployed for server-to-switch connectivity, storage networking, and cloud infrastructure because they provide significantly higher bandwidth than 10G SFP+ while using nearly the same physical form factor and fiber infrastructure.



Why 25G Became the Data Center Standard


Compared with 10G Ethernet, 25G offers several advantages:

  • 2.5× higher bandwidth per server connection

  • Similar cabling and rack density as 10G

  • Better cost per gigabit

  • Lower power consumption than using multiple 10G links

  • Natural building block for higher-speed Ethernet (50G, 100G, 200G, and 400G)


Today, many hyperscale data centers use:

  • 25G to each server

  • 100G uplinks (4 × 25G electrical lanes)

  • 400G spine interconnects


SFP28 Form Factor


SFP28 uses the same mechanical dimensions as SFP+, making upgrades relatively straightforward if the switch hardware supports 25G.


Typical specifications:

Parameter

Value

Data rate

25.78125 Gb/s

Form factor

SFP28

Fiber

Single-mode or multimode

Connector

LC duplex

Hot-pluggable

Yes

Typical power

<1 W for most modules


Common 25G Optical Standards

Standard

Fiber

Distance

Typical Use

25G SR

OM3/OM4 MMF

70–100 m

Server to ToR switch

25G LR

SMF

10 km

Campus and metro

25G ER

SMF

40 km

Long-reach applications

25G BiDi

MMF

70–100 m

Reuse existing duplex MMF


Electrical Interface


Most SFP28 optical modules use:

  • One 25G electrical lane

  • One optical lane

  • NRZ (Non-Return-to-Zero) modulation


Unlike 100G single-lambda optics, 25G SFP28 generally does not require PAM4 or a complex DSP, helping keep latency, power, and cost low.


Advantages


  • High port density

  • Lower power than higher-speed modules

  • Mature ecosystem

  • Wide vendor interoperability (when coding compatibility is supported)

  • Excellent cost per bit


Design Considerations


When deploying 25G optics, consider:

  • Fiber type: Multimode (SR) for short in-rack links; single-mode (LR) for longer campus or inter-building connections.

  • FEC (Forward Error Correction): Many 25G links require RS-FEC or BASE-R FEC depending on the switch ASIC and optics.

  • Compatibility: Ensure switch ports support SFP28 operation and that transceivers are coded appropriately for your vendor if required.

  • Breakout options: Many 100G QSFP28 ports can break out into four independent 25G SFP28 connections.


Typical Data Center Migration Path

Generation

Server Speed

Uplink

Legacy

10G SFP+

40G QSFP+

Current

25G SFP28

100G QSFP28

Emerging

50G SFP56

200G/400G QSFP-DD or OSFP

AI/Hyperscale

100G per server

400G/800G uplinks


Summary


25G SFP28 optics have become the workhorse of modern Ethernet data centers because they balance performance, density, and cost. They enable efficient server connectivity while fitting seamlessly into scalable leaf-spine architectures, and they provide a straightforward migration path toward higher-speed networks built on 100G, 400G, and beyond.


GigOptics - Your Trusted Source for Optics


At GigOptics, we offer a wide range of optical transceivers including all flavors of 25G SFP28 modules; all tested to ensure quality and reliability. For more information, contact us at info@gigoptics.com.

 
 
 
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