Patent ID: 8145055

Claim:
A passive optical network system comprising: a master station to communicate at a first transmission speed and a second transmission speed higher than the first transmission speed; and slave stations including a first slave station that can communicate with the master station through an optical fiber network at the first and the second transmission speeds, and communicates with the master station at a transmission speed selected from the first and the second transmission speeds, wherein the master station includes: an optical level detection section to measure an optical level of a signal received from the first slave station; and a transmission speed determination section that selects the second transmission speed when the measured optical level is a previously determined threshold or higher, selects the first transmission speed when the measured optical level is lower than the previously determined threshold, and transmits a transmission speed instruction indicating the selected first or second transmission speed to the first slave station through the optical fiber network, and wherein the first slave station includes a transmission speed switching control unit to set the transmission speed to communicate with the master station at the first or the second transmission speed according to the transmission speed instruction received from the master station, wherein the signal of which optical level is measured by the optical level detection section is a ranging response signal transmitted from the first slave station in a ranging process, in response to ranging request signals transmitted from the master station in the ranging process to adjust a difference in signal delay amount due to a difference in transmission distance from the master station to respective slave stations.