Dynamic bandwidth allocation apparatus and method and optical line terminal in PON system

An optical line terminal in a PON system, the terminal performing two-way optical communication with a plurality of optical network units through a passive light-splitting node, and relaying an upstream frame received from each optical network unit to an upper network, the terminal comprising:

• a managing unit that manages, for each optical network unit, a reception rate of an upstream frame from the optical network unit, a sending rate of a relay destination of the upstream frame, and a factor representing, by a certain value, a degree of a change in an amount of data occurring in the upstream frame by a relay process varying a frame length of the upstream frame;
• a calculating unit that calculates, based on the reception rate, the sending rate, and the factor, an allocated bandwidth upper limit at which even when the amount of data increases, the upstream frame can be relayed;
• and
• an allocation performing unit that dynamically allocates an amount of upstream transmission for the optical network unit in a range of the calculated allocated bandwidth upper limit.