Connector color coding

IBM® simplex connectors use color-coding to show the direction that light travels through a link (Light propagation in an IBM link). These connectors are black (or use a black marking) and white (or use a white marking).

IBM duplex cable connectors use color-coding to differentiate between multimode and single mode. Multimode cables have black or beige connectors and single mode cables have grey or blue connectors. They do not require color coding to determine the direction that light travels, or propagates, through the cable because the connectors are physically keyed. This provides proper orientation and allows the fibers to be labeled "A" and "B", which is shown on the connector. See Light propagation in an IBM jumper cable.

The SC Duplex connector is an industry standard optical connector (as defined in ANSI Fibre Channel Standard Physical and Signaling Interface (FC-PH), published by the American National Standards Institute. Since it may be purchased from a variety of vendors, there is no consistent scheme of color coding or labeling the ends of a simplex cable with SC Duplex connectors. These connectors can be identified by their shape (Figure 2) and the direction of light propagation must be verified from the vendor specifications. For IBM supplied cables, the single mode SC Duplex jumper has a gray or blue connector and a yellow cable jacket, while the multimode has a black or beige connector with an orange jacket.