Hitachi, Ltd.

Satoshi Konno

Noboru Oosawa

Tohru Kazawa

Makoto Kamijo

It is provided an optical access system, comprising an optical line terminal which is coupled to another network and optical network units which are coupled to the optical line terminal and to a plurality of user terminals. Each of the optical network units obtains a capacity of a buffer included in the each of the optical network unit and a link speed between the each of the optical network units and one of the plurality of user terminals that is coupled to the each of the optical network units; determines a sleep time based on the obtained capacity and the obtained link speed in a case where no communication frames are transmitted for a given period of time from any one of the plurality of user terminals and the optical line terminal; and sets in a sleep state for the determined sleep time.

Optical access system, optical network unit, and optical line terminal

The longest possible sleep time is selected while data missing is prevented in a PON system by referring to the link speeds and the queue buffer capacities of an OLT and ONUs. The OLT calculates a first sleep time candidate based on a first link speed at which the OLT communicates with an upper network and the capacity of an unused area of a first queue buffer where downstream data is held for each of the destination ONUs. Each of the ONUs calculates a second sleep time candidate based on a second link speed at which each of the ONUs communicates with a communication terminal and the capacity of an unused area of a second queue buffer where upstream data bound for the OLT is held. The smaller sleep time is determined and used to change one of the ONUs to a sleep mode.

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Yokohama, Japan

Satoshi Konno