Synchronization and control using out-of-band channels in passive optical network-based systems
Systems and methods are provided to use of out-of-band (OOB) channels for the transport of network-synchronization signals and network control information. These OOB channels transport synchronization and control channels over low-frequency bands outside of the frequency bands used for the data channels. Locating expensive network-synchronization functions in the optical network unit (ONU) and sharing the derived synchronization signals among multiple downstream customer premises equipment (CPE) devices results in cost savings and provides a means for maintaining a continuous, end-to-end synchronization reference, even during periods when the data channels on the copper network segment are in an energy-efficiency mode (e.g., a low-power and/or sleep mode).
1. A subscriber device, comprising:
an optical network unit (ONU), wherein the ONU is configured to:
receive a communication from an optical line terminal (OLT), the communication including synchronization information, control information, and data, and
generate a synchronization signal including the synchronization information; and
a synchronization processor and frequency combiner coupled to the ONU, wherein the synchronization processor and frequency combiner is configured to:
receive the synchronization signal,
generate, using the synchronization signal, an out-of-band (OOB) synchronization signal that oscillates at a frequency and phase determined based on the synchronization information and the control information, and
transmit the OOB synchronization signal to customer premises equipment (CPE) over one or more OOB channels of a physical connection used to carry electrical signals between the ONU and the CPE, wherein the one or more OOB channels are OOB with respect to channels used to carry the data.
2. The subscriber device of claim 1 , wherein the one or more OOB channels are located below a guard band in a frequency spectrum.
3. The subscriber device of claim 2 , wherein the guard band separates a spectrum used for transmitting the one or more OOB channels from a data spectrum used for transmitting data channels to the CPE.
4. The subscriber device of claim 3 , wherein the ONU is further configured to cause the synchronization processor and frequency combiner to transmit the data in the data spectrum.
5. The subscriber device of claim 1 , wherein the one or more OOB channels are located below 276 kHz.
6. The subscriber device of claim 1 , further comprising:
a modem coupled between the ONU and the synchronization processor and frequency combiner.
7. The subscriber device of claim 1 , wherein the synchronization processor and frequency combiner is configured to transmit the OOB synchronization signal to the CPE over the one or more OOB channels via a power splitter coupled to the synchronization processor and frequency combiner.
8. The subscriber device of claim 7 , wherein a second power splitter is coupled to the CPE, and wherein the power splitter is configured to transmit the OOB synchronization signal to the second power splitter over the one or more OOB channels via the physical connection.
9. The subscriber device of claim 1 , wherein the ONU further comprises:
a synchronization and control module configured to generate the synchronization signal.
10. The subscriber device of claim 1 , wherein the OOB synchronization signal is a sine wave.
11. The subscriber device of claim 1 , wherein the synchronization processor and frequency combiner is further configured to determine a time delay between the synchronization processor and frequency combiner and a second synchronization processor and frequency combiner coupled to the CPE.
12. An apparatus, comprising:
a memory; and
processor circuitry, wherein the processor circuitry is configured to:
receive a communication from an optical line terminal (OLT), the communication comprising synchronization information, control information, and data,
generate a data signal based on the data for transmission over one or more data channels of a physical connection used to carry electrical signals between an optical network unit (ONU) and a customer premises equipment (CPE), wherein the data channels are located in a first frequency spectrum, and
generate an out-of-band (OOB) synchronization signal that oscillates at a frequency and phase determined based on the synchronization information and the control information for transmission over one or more OOB channels of the physical connection, wherein the one or more OOB channels are located OOB, with respect to the data channels, in a second frequency spectrum.
13. The apparatus of claim 12 , wherein the second frequency spectrum is below the first frequency spectrum.
14. The apparatus of claim 12 , wherein a guard band separates the first frequency spectrum from the second frequency spectrum.
15. The apparatus of claim 12 , wherein the synchronization information comprises frequency information, phase information, and time of day information.
16. The apparatus of claim 12 , wherein the control information includes operations, administration, and maintenance (OAM) information and link control messaging.
17. A method, comprising:
receiving a communication from an optical line terminal (OLT), the communication comprising synchronization information, control information, and data; and
generating an out-of-band (OOB) synchronization signal that oscillates at a frequency and phase determined based on the synchronization information and the control information; and
transmitting the OOB synchronization signal to customer premises equipment (CPE) over one or more OOB channels of a physical connection used to carry electrical signals between the OLT and the CPE, wherein the one or more OOB channels are located OOB, with respect to data channels used to carry the data, in a first frequency spectrum.
18. The method of claim 17 , further comprising:
transmitting the data over the data channels, wherein the data channels are located in a second frequency spectrum.
19. The method of claim 18 , wherein the one or more OOB channels are located below a guard band separating the first frequency spectrum from the second frequency spectrum.
20. The method of claim 17 , wherein the first frequency spectrum comprises frequencies below 276 kHz.