The invention provides a data optical fiber cascading apparatus and system. The apparatus comprises: a synchronous clock input module used for receiving a synchronous clock electric signal of an external synchronous clock source; a core processing module used for transmitting the synchronous clock electric signal to a synchronous clock output module, or converting a synchronous clock optical signal transmitted by an optical fiber interface module into an electric signal, or converting an external synchronous clock electric signal into an optical signal; the synchronous clock output module used for transmitting the synchronous clock electric signal of the external synchronous clock source to a synchronous clock use device, or transmitting the electric signal converted from the synchronous clock optical signal to the synchronous clock use device; the optical fiber interface module used for receiving the external synchronous clock optical signal, and transmitting the optical signal to the core processing module, or sending the synchronous clock optical signal sent by the core processing module; and the synchronous clock input module comprises a plurality of input interfaces, and the output module comprises a plurality of output interfaces. The above schemes is simple to synchronize the signals, high in efficiency and low in cost.