Orthogonal frequency division multiplexing passive optical network system

The invention provides an orthogonal frequency division multiplexing passive optical network system, which modulates an uplink data stream by using orthogonal frequency division multiplexing (OFDM) on the basis of not increasing hardware cost and media access control (MAC) complexity. The system adopts OFDM modulation for both uplink transmission and downlink transmission. In the OFDM modulation of uplink data, the positions and bandwidths of frequency bands allocated to each optical network unit and used for bearing valid uplink data in the whole converged OFDM frequency band are variable. Different frequency bands are allocated to uplink channels of different optical nodes, so that the frequency bands allocated to all the ONUs in the system and used for bearing the valid uplink data are positioned at different positions of the whole OFDM frequency spectrum, and are not overlapped with one another. An uplink transmission module can perform adaptive source configuration, dynamically allocate the number of sub-carriers according to the traffic of a user and regulate the bandwidths of the frequency bands used for bearing the valid uplink data.