An optical line terminal, OLT, device, comprising an interface unit and a service processing apparatus, wherein: the interface unit is configured to: receive data in an Ethernet format transmitted by the service processing apparatus, perform protocol processing on the received data in the Ethernet format, convert the data after protocol processing into a transmission signal corresponding to a sending interface and then transmit the transmission signal to an external device, as well as receive message data sent by the external device, and convert the message data for protocol processing corresponding to the service processing apparatus, and convert a signal after the protocol processing into data in the Ethernet format, and transmit the data to the service processing apparatus; and the service processing apparatus is configured to: perform service processing on the data transmitted by the interface unit, and transmit the processed data to the interface unit; wherein, the service processing apparatus comprises a core area, a backplane area, a power supply area, and a fan area, characterized by that, the core area is configured to: perform service processing on the signal transmitted by the interface unit, and transmit the processed signal to the interface unit through a serial standard Ethernet interface, as well as implement data transmission between various services through the backplane area; the core area comprises a pass-through daughter card, a low-speed switch daughter card and a high-speed switch daughter card, wherein: the pass-through daughter card is configured to: communicate with each switch daughter card, and the switch daughter card comprises a low-speed switch daughter card and a high-speed switch daughter card; the high-speed switch daughter card is configured to: perform a basic communication function between each switch daughter card, and process information carried in messages sent to the external device; and the low-speed switch daughter card is configured to: perform an encapsulation and conversion on the messages in the backplane area, and implement data exchange between each switch daughter card. the interface unit is configured to: receive data in an Ethernet format transmitted by the service processing apparatus, perform protocol processing on the received data in the Ethernet format, convert the data after protocol processing into a transmission signal corresponding to a sending interface and then transmit the transmission signal to an external device, as well as receive message data sent by the external device, and convert the message data for protocol processing corresponding to the service processing apparatus, and convert a signal after the protocol processing into data in the Ethernet format, and transmit the data to the service processing apparatus; and the service processing apparatus is configured to: perform service processing on the data transmitted by the interface unit, and transmit the processed data to the interface unit; wherein, the service processing apparatus comprises a core area, a backplane area, a power supply area, and a fan area, the core area is configured to: perform service processing on the signal transmitted by the interface unit, and transmit the processed signal to the interface unit through a serial standard Ethernet interface, as well as implement data transmission between various services through the backplane area; the core area comprises a pass-through daughter card, a low-speed switch daughter card and a high-speed switch daughter card, wherein: the pass-through daughter card is configured to: communicate with each switch daughter card, and the switch daughter card comprises a low-speed switch daughter card and a high-speed switch daughter card; the high-speed switch daughter card is configured to: perform a basic communication function between each switch daughter card, and process information carried in messages sent to the external device; and the low-speed switch daughter card is configured to: perform an encapsulation and conversion on the messages in the backplane area, and implement data exchange between each switch daughter card. the pass-through daughter card is configured to: communicate with each switch daughter card, and the switch daughter card comprises a low-speed switch daughter card and a high-speed switch daughter card; the high-speed switch daughter card is configured to: perform a basic communication function between each switch daughter card, and process information carried in messages sent to the external device; and the low-speed switch daughter card is configured to: perform an encapsulation and conversion on the messages in the backplane area, and implement data exchange between each switch daughter card.