400G, 800G and 1.6T: Choosing the Right Transceiver for Your AI Fabric

As AI training clusters scale, the optical transceiver has become one of the most critical — and cost-sensitive — components in the network. This guide covers the key decisions when selecting compatible transceivers for 400G, 800G and next-generation 1.6T fabrics. ## Speed and form factor 400G optics are commonly available in QSFP-DD and OSFP form factors. 800G introduces OSFP and QSFP-DD800. 1.6T brings OSFP-XD and beyond. ## Vendor compatibility Compatible transceivers must be correctly coded for the target platform. A transceiver coded for NVIDIA Spectrum may not behave identically on an Arista or Cisco switch. Always verify compatibility against the vendor and platform family. ## Reach and fibre type Match the transceiver reach (DR, FR, LR) and fibre type (SMF vs MMF) to your physical link distance. ## Testing Look for suppliers that test every unit before dispatch. Tested optics reduce deployment risk in production AI fabrics.