Subscriber-side optical communication device, communication system, control device, and power-saving control method

A communication system comprising:

• a station-side optical communication device;
• and
• a subscriber-side optical communication device that performs transmission and reception of an optical signal with the station-side optical communication device, wherein
• the subscriber-side optical communication device include
• an optical transmission-and-reception module including a receiver and a transmitter that are configured to enter into a power-saving state separately, the optical transmission-and-reception module performing transmission and reception of a signal with the station-side optical communication device,
• a clock regeneration unit that regenerates a clock based on a signal from the station-side optical communication device received by the optical transmission-and-reception module and supplies the clock,
• an internal clock source that generates an internal clock and supplies the internal clock,
• a time management unit that manages a time of the subscriber-side optical communication device based on the clock in a period in which the clock regeneration unit supplies the clock and manages the time of the subscriber-side optical communication device based on the internal clock in a period in which the clock regeneration unit does not supply the clock, and
• a sleep-time control unit that decides, when a power-saving mode for causing the receiver to enter into a power-saving state for a predetermined sleep time is set, a receiver-time synchronization time that is a period in which the receiver is normally operated within the sleep time, based on a difference between predetermined information indicating a time in the station-side optical communication device included in the signal transmitted from the station-side optical communication device and the time managed by the time management unit, and notifies the receiver-time synchronization time to the station-side optical communication device, wherein
• the station-side optical communication device instructs a new sleep time for the receiver, which is reduced by the notified receiver-time synchronization time, to the subscriber-side optical communication device.

A control device for a subscriber-side optical communication device including an optical transmission-and-reception module that performs transmission and reception of a signal with a station-side optical communication device and a clock regeneration unit that regenerates a clock based on a signal from the station-side optical communication device received by the optical transmission-and-reception module and supplies the clock, the subscriber-side optical communication device configured to cause a receiver and a transmitter constituting the optical transmission-and-reception module to enter into a power-saving state separately, the control device comprising:

• an internal clock source that generates an internal clock and supplies the internal clock;
• a time management unit that manages a time of the subscriber-side optical communication device based on the clock in a period in which the clock regeneration unit supplies the clock and manages the time of the subscriber-side optical communication device based on the internal clock in a period in which the clock regeneration unit does not supply the clock;
• a sleep-time control unit that decides, when a power-saving mode for causing the receiver to enter into a power-saving state for a predetermined sleep time is set, a receiver-time synchronization time that is a period in which the receiver is normally operated within the sleep time, based on a difference between predetermined information indicating a time in the station-side optical communication device included in the signal transmitted from the station-side optical communication device and the time managed by the time management unit;
• and
• a power-saving control unit that controls the receiver to be normally operated in the receiver-time synchronization time during the sleep time.

A power-saving control method for a subscriber-side optical communication device including an optical transmission-and-reception module that performs transmission and reception of a signal with a station-side optical communication device, the subscriber-side optical communication device configured to cause a receiver and a transmitter constituting the optical transmission-and-reception module to enter into a power-saving state separately, the power-saving control method comprising:

• a clock regeneration step of regenerating a clock based on a signal from the station-side optical communication device received by the optical transmission-and-reception module and supplying the clock;
• an internal-clock generation step of generating an internal clock and supplying the internal clock;
• a time management step of managing a time of the subscriber-side optical communication device based on the clock in a period in which the clock is supplied at the clock regeneration step and manages the time of the subscriber-side optical communication device based on the internal clock in a period in which the clock is not supplied at the clock regeneration step;
• a sleep-time control step of deciding, when a power-saving mode for causing the receiver to enter into a power-saving state for a predetermined sleep time is set, a receiver-time synchronization time that is a period in which the receiver is normally operated within the sleep time, based on a difference between predetermined information indicating a time in the station-side optical communication device included in the signal transmitted from the station-side optical communication device and the time managed at the time management step;
• and
• a power-saving control step of controlling the receiver to be normally operated in the receiver-time synchronization time during the sleep time.