The present disclosure relates to the field of optical communications. A board is disclosed. The board includes a level adjustment circuit, a detection apparatus, and a control apparatus. The detection apparatus is configured to: when the detection apparatus is connected to an optical module, receive an indication signal output by an upstream optical signal detection pin; continuously detect a received first level signal and the received indication signal. If there is a second level signal, opposite to the first level signal, the detection apparatus notifies the control apparatus that the optical module is inserted. If there is no second level signal in the signal received within the preset duration, the detection apparatus notifies the control apparatus that the optical module is absent. This makes the optical module less dependent on the in-position pin, and decreases a quantity of pins of the optical module.