Overview
The twin-port transceiver is a key innovation for expanding the 400GbE Spectrum-4 Ethernet (400G EN) switch capabilities. The line rate is 400Gb/s based on the 100G-PAM4 modulation. The switch uses Twin port OSFP cages supporting two transceiver engines in a single OSFP form-factor plug creating 800Gb/s electrical to the switch and 2x400G optics using two MPO/-12/APC optical connectors. The switch uses the Twin port, 2x400G OSFP plugs for transceivers, copper DACs and ACCs, and are only used in Spectrum-4 OSFP air-cooled switches.
The twin-ports enable several unique configurations to connect switches to switches, ConnectX-7 adapters, and BlueField-3 DPUs.
The Twin port OSFP uses two, 4-channel MPO-12/APC optical connectors with two 4-channel fiber cables. These can link to a single port 400G OSFP or QSFP112 transceivers used in ConnectX-7 adapters and/or BlueField-3 DPUs.
The electronics, optics and optical connectors are the same for both single port OSFP and QSFP112. Both ConnectX-7 and BlueField-3 devices can be used with Twin port OSFP transceivers at the same time with their respective form-factor type.
Twin-port multimode OSFP transceivers remain at 15 Watts for all configurations linking OSFP switches, OSFP and QSFP112 adapters, and DPUs simultaneously.
Linking Twin-port transceivers with 1:2 fiber splitter cables to 400G transceivers automatically creates 200Gb/s transceivers by activating only 2-channels and automatically reduces power consumption in the 400G transceiver from 8 to 5.5 Watts.
Twin-Port transceivers require ordering two fibers at specific lengths required
Each fiber cable can each be different lengths. Both fibers need to be same type: both straight or both splitters, and not mixed.
Both fibers should be the approximately same length to avoid inducing different latency delays in the fibers (4.5ns/meter).
Straight and splitter fibers cannot be used at the same time in Twin port OSFP transceivers.
NVIDIA supplies multimode, crossover, straight fiber cables up to 100-meters straight and 50-meters for splitters that enable linking transceivers directly together.
All combinations of Twin port 2x400G OSFP, 400G single port OSFP/QSFP112, ConnectX-7 and BlueField-3 contains both InfiniBand and Ethernet protocols which is activated upon inserting into an InfiniBand or Ethernet switch. This enables one set of cables, transceivers, adapters and DPUs to have multiple uses in a network – especially in DGX systems where low-latency InfiniBand switching may be used for GPU-to-GPU networking and Ethernet switching systems for storage and cluster communication.
The use cases include:
Switch-to-switch at 800Gb/s or to two switches at 400Gb/s
Switch-to-two combinations of 400G ConnectX-7 BlueField-3
Switch-to-four combinations of 200G ConnectX-7 and/or BlueField-3
Switch linked to the DGX H100