As data transfer rates supported by the PCIe protocol are increasing, it is getting exceedingly hard to enable them over copper wires over longer distances. On Wednesday PCI-SIG announced formation of the PCI-SIG Optical Workgroup, which will prep PCIe for using optical interconnects. Over time PCIe optical interconnects will be particularly beneficial for artificial intelligence, datacenter, and high-performance computing applications.
Implementation of extended PCIe 5.0 (32 GT/s) connections in servers requires usage of PCIe 5.0 retimers due to signal degradation over increased distances, which generally reduces trace lengths of PCIe 5.0 interconnects when compared to older specifications. This distance can fluctuate based on the selection of materials and environmental conditions, but, in general, PCIe 5.0 retimers are common in modern AI and HPC machines. The challenge of signal integrity over copper interconnections becomes even more pronounced with the future introduction of PCIe 6.0 at 64 GT/s and PCIe 7.0 at 128 GT/s, which is why PCI-SIG is exploring alternatives in the form of optical interconnects.
