An apparatus and a method for detecting an uplink optical signal. The apparatus includes a memory and a processor, where the processor is configured to determine a remaining bandwidth in a target uplink frame as a test window, where the remaining bandwidth in the target uplink frame indicates an unallocated bandwidth in the target uplink frame, and detect an uplink optical signal in the determined test window. Therefore, a remaining bandwidth obtained after bandwidth allocation in a target uplink frame is used to detect an uplink optical signal, which can effectively use a resource without the need of independently opening a test window and using an extra resource to detect the uplink optical signal, thereby avoiding waste of a resource and improving test efficiency.