25GBASE-SR Application Overview



25GBASE‑SR: 25 Gb/s serial transmission at 850 nm over 2 multimode optical fibers, with reach up to at least 100 m

25GBASE‑SR supports short wavelength serial transmission over duplex (2‑fiber) multimode optical fiber cabling. The application’s nominal symbol rate is 25.78125 GBd per lane and the supported distance varies according to the type of multimode cable used. Network equipment interface connections include a duplex optical fiber connector and a standard socket into which physical (PHY) layer transceiver modules may be plugged.

  • Connector type: LC
  • Transceiver module: SFP28
  • Defined in clause 112 of the IEEE 802.3 Standard for Ethernet
  • Initially published as IEEE Std 802.3by™: Media Access Control Parameters, Physical Layers, and Management Parameters for 25 Gb/s Operation in 2016

Optical Fiber Cabling (Channel) Characteristics:

Parameter OM3 OM4 OM5 Unit
Operating wavelength: 850 nm
Modal bandwidth (min): 2,000 4,700 MHz∙km
Operating range: 0.5 to 70 0.5 to 100 m
Insertion loss (max): 1.8 1.9 dB

Key Application Capabilities:

  • Defines a 25 Gb/s PHY for operation over at least 100 m of MMF
  • Supports full-duplex operation only
  • Preserves the Ethernet frame format utilizing the Ethernet MAC
  • Preserves minimum and maximum FrameSize of current 802.3 Standard for Ethernet
  • Provides appropriate support for optical transport networks (OTNs)
  • Supports a BER of better than or equal to 10-12 at the MAC/PLS service interface (or the frame loss ratio equivalent)
  • Supports optional Energy-Efficient Ethernet operation

Related Applications:

The IEEE P802.3by Task Force also specified the following 25 Gb/s Ethernet applications:

Application    Operating    Wavelength Media Operating Range
25GBASE-CR Copper Twinax up to 5 m1
25GBASE-KR Backplane
1 Supported distance varies according to Reed Solomon Forward Error Correction (RS-FEC) implementation.

Back to TIA FOTC IEEE 802.3 Multimode Optical Fiber Ethernet Standards Explorer