Use a single-mode fiber jumper for a single-mode optical module. Determine the optical connector type based on the interface type. Unidirectional single-fiber communication enables a device to send but not receive packets or, conversely, to receive but not send packets. Enter system view, return user view with return command. A single fiber means that two optical modules are connected by only one fiber, and unidirectional communication means that packets can be sent in only one. A switch must use optical or copper modules that have been certified for use on Huawei switches. Non-certified optical or copper modules cannot ensure transmission reliability and may affect service stability.