400GBASE-SR8 Application Overview


400GBASE-SR8: 400 Gb/s PAM4 parallel transmission at 850 nm over 16 multimode optical fibers, with reach up to at least 100 m

400GBASE-SR8 supports short wavelength 4‑level pulse amplitude modulated (PAM4) parallel transmission over eight lanes (16‑fibers) of multimode optical fiber cabling. The application’s equivalent symbol rate is 53.125 GBd per lane (PAM4 maps pairs of bits into a single symbol) and the supported distance varies according to the type of multimode cable used. Network equipment interface connections include a multi‑fiber push on (MPO) connector and standard sockets into which a physical (PHY) layer transceiver module may be plugged.

  • Connector type: MPO/MTP
  • Transceiver module: QSFP-DD, OSFP
  • Defined in clause 138 of the IEEE 802.3 Standard for Ethernet
  • Initially published as IEEE Std 802.3cm: Physical Layer and Management Parameters for 400 Gb/s over Multimode Fiber in 2020

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
Cabling skew (max): 79 ns
Cabling skew variation: 2.4 ns

Key Application Capabilities:

  • Defines an eight-lane 400 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 10-13 at the MAC/PLS service interface (or the frame loss ratio equivalent)
  • Supports optional Energy-Efficient Ethernet operation

Related Applications:

The IEEE P802.3cm Task Force also specified the following PAM4, 26.5625 GBd symbol rate 400 Gb/s Ethernet application:

Application    Operating    Wavelength Media Operating Range1
400GBASE-SR4.2 two WDM2 Multimode up to 150 m
1 Supported distance varies according to the type of optical fiber cable used.
2 850 nm and 910 nm

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