Aboard of an optical line terminal OLT, wherein the board comprises a level adjustment circuit, a detection apparatus, and a control apparatus, the level adjustment circuit is electrically connected to an input end of the detection apparatus, the input end of the detection apparatus and the level adjustment circuit are further configured to be connected to an upstream optical signal detection pin of an optical module, an output end of the detection apparatus is connected to an input end of the control apparatus, and an output end of the control apparatus is configured to be connected to the optical module, wherein: the control apparatus is configured to send a reset signal to the optical module at regular intervals of a first preset period; the level adjustment circuit is configured to: when the detection apparatus is disconnected from the optical module, output a first level signal to the detection apparatus; and the detection apparatus is configured to: when the detection apparatus is connected to the optical module, receive an indication signal output by the upstream optical signal detection pin, and is further configured to continuously detect the received first level signal and indication signal, wherein when there is a second level signal, opposite to the first level signal, in a signal received within preset duration, the detection apparatus notifies the control apparatus that the optical module is inserted; or when 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, wherein the preset duration is greater than the first preset period, wherein the level adjustment circuit comprises: - a pull-up circuit, wherein the first level signal is a high-level signal and the second level signal is a low-level signal; or - a pull-down circuit, wherein the first level signal is a low-level signal and the second level signal is a high-level signal. the control apparatus is configured to send a reset signal to the optical module at regular intervals of a first preset period; the level adjustment circuit is configured to: when the detection apparatus is disconnected from the optical module, output a first level signal to the detection apparatus; and the detection apparatus is configured to: when the detection apparatus is connected to the optical module, receive an indication signal output by the upstream optical signal detection pin, and is further configured to continuously detect the received first level signal and indication signal, wherein when there is a second level signal, opposite to the first level signal, in a signal received within preset duration, the detection apparatus notifies the control apparatus that the optical module is inserted; or when 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, wherein the preset duration is greater than the first preset period, wherein the level adjustment circuit comprises: - a pull-up circuit, wherein the first level signal is a high-level signal and the second level signal is a low-level signal; or - a pull-down circuit, wherein the first level signal is a low-level signal and the second level signal is a high-level signal. - a pull-up circuit, wherein the first level signal is a high-level signal and the second level signal is a low-level signal; or - a pull-down circuit, wherein the first level signal is a low-level signal and the second level signal is a high-level signal. <EOS>