Data communication method for optical network system, optical line terminal and optical network system

Provided in the present invention are a data communication method for an optical network system, an optical line terminal and an optical network system, said method comprising: transmitting a downlink message to an optical network terminal via a first port of the optical line terminal; receiving an uplink message returned from the optical network terminal via a second port of the optical line terminal, and obtaining a second time at which the uplink message was received, and obtaining a first time at which the uplink message arrived at the first port; according to the first time and the second time, obtaining the equalized delay between the second port and the optical network terminal; when the optical line terminal is switched from the first port to the second port, the optical line terminal sends the equalized delay via the second port, and communicates data with the optical network terminal via the second port. By using the data communication method of the present optical network system, and the optical line terminal and the optical network system provided by the present invention, the ports can be switched quickly, thus maximally reducing processing time and improving system stability.