OCuLink stands for “Optical Copper (Cu) Link” and is a PCI Express (PCIe) interconnect system. It was created by the standards body for the PCI interface (PCI-SIG) and the latest OCuLink 2 is considered an alternative to Thunderbolt. OCuLink 2 will have up to 16 GT/s (8 GB/s total for x4 lanes).

It features a small cable form factor that is optimized for internal and external enclosure usage and is capable of providing up to 32 Gbps in each direction within a four lane configuration. The OCuLink 2 connectors work as a two-piece, metal-to-metal contact system with Molex’s NanoPitch connector and cable assembly system. The cable doesn’t carry clock signals or power, which allows for low-cost cables, connectors, and ports due to the lack of complex shielding requirements.

Usage for OCuLink include internal and external PCIe attached storage, PCIe I/O expansion, and A/V equipment. In server applications, it is being used as a connection from the motherboard or add-in-card to HDD midplane, an alternative to HDminiSAS. With NVMe U.2 drives, the OCuLink protocol can be used over the U.2 connector.