Optical network unit power management in passive optical networks

1. A method of optical communication in a passive optical network, comprising:

operating an optical network unit (ONU) in a first state in which a transmitter of the ONU is turned off and a receiver of the ONU is turned on;

operating the ONU in a second state in which both the transmitter and the receiver are turned off;

transitioning the ONU directly from the first state to the second state and transitioning the ONU directly from the second state to the first state, based on a power management rule;

ensuring the ONU is fully powered up, synchronized, and capable of responding to both upstream and downstream traffic and control before exiting the first state or the second state; and

receiving, by the receiver, a power management message from an optical line terminal (OLT); and

changing the power management rule based on the received power management message.

2. The method of claim 1 , further comprising:

operating the ONU in a third state in which both the transmitter and the receiver are turned on.

3. The method of claim 1 , wherein the power management rule specifies a first time period for operation in the first state and a second time period for operation in the second state and wherein the transitioning is performed upon expiration of at least one of the first time period and the second time period.

4. The method of claim 1 , further comprising:

transmitting, to an optical line terminal, a message indicative of the transitioning between the first state and the second state.

5. The method of claim 1 , further comprising:

performing the transitioning responsive to the received power management message and a local decision to change an operational state.

6. An optical communication apparatus in a passive optical network, comprising:

means for operating an optical network unit (ONU) in a first state in which a transmitter of the ONU is turned off and a receiver of the ONU is turned on;

means for operating the ONU in a second state in which both the transmitter and the receiver are turned off;

means for transitioning the ONU directly from the first state to the second state and means for transitioning the ONU directly from the second state to the first state, based on a power management rule;

means for ensuring the ONU is fully powered up, synchronized, and capable of responding to both upstream and downstream traffic and control before exiting the first state or the second state; and

means for receiving, by the receiver, a power management message from an optical line terminal; and

means for changing the power management rule based on the received power management message.

7. The apparatus of claim 6 , further comprising:

means for operating the ONU in a third state in which both the transmitter and the receiver are turned on.

8. The apparatus of claim 6 , wherein the power management rule includes a first time period for operation in the first state and a second time period for operation in the second state and wherein the means for transitioning performs a state transition upon expiration of at least one of the first time period and the second time period.

9. The apparatus of claim 6 , further comprising:

means for receiving a power management message from an optical line terminal; and

means for performing the transitioning responsive to the received power management message and a local decision to change an operational state.

10. An optical communication apparatus, comprising:

a memory that stores processor-executable instructions; and

a processor that uses the stored instructions to implement a method, comprising operating an optical network unit (ONU) in a first state in which a transmitter of the ONU is turned off and a receiver of the ONU is turned on; and operating the ONU in a second state in which both the transmitter and the receiver are turned off; and

wherein the processor includes means for transitioning the ONU directly from the first state to the second state and means for transitioning the ONU directly from the second state to the first state, based on a power management rule;

wherein the processor uses stored instructions to ensure the ONU is fully powered up, synchronized, and capable of responding to both upstream and downstream traffic and control before exiting the first state or the second state; and

wherein the processor further uses the stored instructions to implement the method by receiving, by the receiver, a power management message from an optical line terminal (OLT) and changing the power management rule based on the received power management message.

11. The apparatus as in claim 10 , wherein the power management rule specifies a first time period for operation in the first state and a second time period for operation in the second state and wherein the transitioning is performed upon expiration of at least one of the first time period and the second time period.

12. An optical line terminal (OLT) for operation in a passive optical network (PON), the optical line terminal comprising:

a processor configured to generate messages for controlling a transition of an optical network unit from a first low power state in which a receiver of the optical network unit is turned on but a transmitter of the optical network unit is turned off to a second low power state in which both the receiver and the transmitter of the optical network unit are turned off;

a transmitter configured to transmit the generated messages to the optical network unit;

wherein the generated messages comprises a periodic consent message to allow the optical network unit to remain in either the first low power state or the second low power state.

13. The optical line terminal as in claim 12 , wherein the processor includes means for specifying a first time period for operation in the first low power state and a second time period for operation in the second low power state and wherein the transition of the optical network unit from the first low power state to the second low power state is controlled to occur upon expiration of at least one of the first time period and the second time period.

14. A passive optical network (PON) communications system, comprising:

an optical network unit (ONU) operable in a first low power mode in which the ONU is able to receive but not transmit and a second low power mode in which the ONU is not able to either receive or transmit, wherein the ONU is configured to transition from the first low power mode to the second low power mode and to transition from the second low power mode to the first low power mode based on a power management rule, and wherein the ONU changes a power management rule based on a received power management message;

an optical line terminal (OLT) communicably coupled to the ONU, the OLT configured to transmit a control message to the ONU to control at least one aspect of transition of the ONU between the first low power mode and the second low power mode; and

the ONU configured to ensure that the ONU is fully powered up, synchronized, and capable of responding to both upstream and downstream traffic and control before exiting the first low power mode or the second low power mode.

15. The system as in claim 14 , wherein:

the OLT is configured to transmit the control message that includes the power management rule that specifies a first time period for operation in the first low power state and a second time period for operation in the second low power state and to control the ONU to transition from the first low power state to the second low power state upon expiration of at least one of the first time period and the second time period.