The Twin-port transceiver is a key innovation for expanding the 400G NDR InfiniBand Quantum-2 and 400GbE Spectrum-4 Ethernet (400G IB/EN) switch capabilities. The line rate is 400Gb/s for both 400GbE Ethernet and NDR InfiniBand based on the 100G-PAM4 modulation. The switches use Twin port OSFP cages supporting two transceiver engines in a single OSFP form-factor plug creating 800Gb/s electrical to the switch and 2x400G multiplexed optics using duplex LC optical connectors.
Each LC-based fiber cable can link to another 2xFR4 transceiver transferring 800Gb/s or to two separate 2xFR4s in separate switches at 400Gb/s for a total of three switches linked. Additionally, since the LC fiber cables send 4x100G-PAM4 CWDM4 signals, they can also link to 400G FR4 QSFP-DD transceivers there by enabling bridging 50G-PAM4 Spectrum-3 to 100G-PAM4 Spectrum-4 Ethernet systems.
The primary use case for the MMS4X50-NM transceiver is to link multiple switches together up to 2km reaches.
FR4 CWDM4 multiplexing combines 4 different wavelength laser data signals into a single fiber which is filtered back to 4 in the receiving transceiver.
Used for long fiber runs and in complex fiber infrastructures to save fiber costs.
Linking two transceivers directly together, the LC fibers must be crossed over to align transmit lasers with receive photodetectors.
Twin-Port transceivers require ordering two fibers at specific lengths. NVIDIA does not supply these fibers.
Fiber splitters cannot be used with CWDM4 transceivers, as the wavelengths are multiplexed together into one fiber.
Both fibers should be the approximately same length to avoid inducing different latency delays in the fibers (4.5ns/meter).
The use cases include:
Switch-to-switch at 800Gb/s
This configuration enables transferring 800Gb/s between two switches using a single transceiver in each switch. The 2xFR4 supports both InfiniBand and Ethernet and can link two InfiniBand Quantum-2 switches or two Ethernet SN5600 switches together using only 4 fibers in total. Additionally, one 800G switch can link two switches at 400G using separate fiber to each 2xFR4 in the switches.
800G switch-to-two QSFP-DD switches at 400Gb/s
A 2xFR4 Twin port OSFP transceiver can have each 400G fiber cable sent to two QSFP-DD FR4 transceivers as both operate optically at 100G-PAM4. This enables 8x50G-PAM4 electrical Spectrum-3 Ethernet SN4700 QSFP-DD switches to link to a 64-port Ethernet SN5600 Spectrum-4 Twin port OSFP switch. Additionally, each 400G FR4 could be inserted into two different QSFP-DD switches.
The 400G FR4 QSFP-DD transceiver employs an 8x50G-PAM4 electrical side and uses an internal “gearbox” IC to translate to 4x100G-PAM4 optical which can link to the 2xFR4 Twin port OSFP..