Data synchronization in optical networks and devices
Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can then process data received from the transmitter in a manner synchronous to the manner in which the data was transmitted by the transmitter.
1. An apparatus, comprising:
an analog to digital conversion circuitry operable to receive data comprising frames and output digitized data corresponding to the received data; and
a digital signal processor operable to:
receive the digitized data from the analog to digital conversion circuitry;
determine a location of a frame header associated with one of the frames, the location having a probability that satisfies a probability threshold; and
estimate a frequency offset associated with the digitized data using the location of the frame header,
wherein the digital signal processor comprises an AND logic circuit operable to receive confirmation data associated with each subcarrier in the digitized data and to set a barrel shifter flag to a first value when confirmation data for each subcarrier indicates that a framer index estimation associated with the subcarrier is confirmed.
2. The apparatus of claim 1 , wherein:
the digital signal processor is operable to estimate the frequency offset based on a complex value of a cross correlation at the location of the frame header associated with the one of the frames in the digitized data; and
the received data is synchronized with data transmission from a transmitter of the received data based on the frequency offset.
3. The apparatus of claim 1 , wherein the digital signal processor comprises a barrel shifter operable to receive a signal indicative of the barrel shifter flag set by the AND logic circuit and to perform a shift operation if the barrel shifter has the first value.
4. The apparatus of claim 3 , wherein the barrel shifter is operable to compensate the determined location of the frame header in the digitized data such that an order of framer indices associated with subcarriers in the digitized data is the same as an order of framer indices implemented by a transmitter that transmitted the data over an optical network and received by the analog to digital conversion circuitry.
5. The apparatus of claim 1 , wherein the digital signal processor is operable to generate a first indicator indicating that the location of the frame header is determined.
6. The apparatus of claim 1 , wherein:
the digital signal processor is operable to generate a lock indicator signal or set a lock indicator to a first value to indicate that the location of the frame header is determined; and
the frequency offset is estimated in response to generating the lock indicator signal or setting the lock indicator to the first value.
7. The apparatus of claim 1 , wherein the data comprising frames is associated with information carried by at least one optical subcarrier provided to circuitry coupled to the analog to digital conversion circuitry.
8. The apparatus of claim 1 , wherein the apparatus is a receiver provided in a transceiver.
9. An apparatus, comprising:
an analog to digital conversion circuitry operable to receive data comprising frames and output digitized data corresponding to the received data; and
a digital signal processor operable to:
receive the digitized data from the analog to digital conversion circuitry;
determine a location of a frame header associated with one of the frames, the location having a probability that satisfies a probability threshold; and
estimate a frequency offset associated with the digitized data using the location of the frame header, wherein:
the digitized data is provided through one or more subcarriers; and
the digital signal processor is operable to compensate a determined location of a frame header for each of the one or more subcarriers in the digitized data such that an order of framer indices for the one or more subcarriers is the same as an order of framer indices implemented by a transmitter that transmitted the data over an optical network and received by the analog to digital conversion circuitry.
10. An apparatus, comprising:
an analog to digital conversion circuitry operable to receive data comprising frames and output digitized data corresponding to the received data; and
a digital signal processor operable to:
receive the digitized data from the analog to digital conversion circuitry;
determine a location of a frame header associated with one of the frames, the location having a probability that satisfies a probability threshold; and
estimate a frequency offset associated with the digitized data using the location of the frame header, wherein the digital signal processor comprises:
a quantizer to quantize the digitized data; and
a soft framer circuit to receive the quantized digitized data from the quantizer and determine the location of the frame header.
11. An apparatus, comprising:
an analog to digital conversion circuitry operable to receive data comprising frames and output digitized data corresponding to the received data; and
a digital signal processor operable to:
receive the digitized data from the analog to digital conversion circuitry;
determine a location of a frame header associated with one of the frames, the location having a probability that satisfies a probability threshold; and
estimate a frequency offset associated with the digitized data using the location of the frame header, wherein the digital signal processor is operable to determine the location of the frame header based on estimating locations of frame headers for a plurality of frames in the digitized data.
12. A receiver operable to communicate with a transmitting device over an optical network, the receiver comprising:
an optics circuit configured to receive a signal comprising subcarrier signals, each of the subcarrier signals comprising a data frame that comprises (i) a frame header comprising framer symbols and a first set of pilot symbols, and (ii) a payload comprising payload symbols and a second set of pilot symbols;
a digital signal processor operable, for each of one or more subcarrier signals respectively, to:
determine a location of a frame header of the data frame in the subcarrier signal; and
estimate a frequency offset associated with the data frame using the location of the frame header.
13. The receiver of claim 12 , wherein:
the digital signal processor is operable to estimate the frequency offset based on a complex value of a cross correlation at the location of the frame header of the data frame; and
the received signal is synchronized with data transmission from a transmitter of the received data based on the frequency offset.
14. The receiver of claim 12 , wherein the digital signal processor comprises an AND logic circuit operable to receive confirmation data associated with each of the one or more subcarrier signals and to set a barrel shifter flag to a first value when confirmation data for each of the one or more subcarrier signals indicates that a framer index estimation associated with the subcarrier signal is confirmed.
15. The receiver of claim 14 , wherein the digital signal processor comprises a barrel shifter operable to receive a signal indicative of the barrel shifter flag set by the AND logic circuit and to perform a shift operation if the barrel shifter has the first value.
16. The receiver of claim 15 , wherein the barrel shifter is operable to compensate the determined location of the frame header such that an order of framer indices associated with the subcarrier signals is the same as an order of framer indices implemented by a transmitter that transmitted the data over an optical network and received by the optics circuit.
17. The receiver of claim 12 , wherein:
the digital signal processor is operable to compensate a determined likely location of a frame header for each subcarrier signal such that an order of framer indices for the subcarrier signals is the same as an order of framer indices implemented by a transmitter that transmitted the data over an optical network and received by the optics circuit.
18. The receiver of claim 12 , wherein:
the digital signal processor is operable to generate a lock indicator signal or set a lock indicator to a first value to indicate that the location of the frame header is determined; and
the frequency offset is estimated in response to generating the lock indicator signal or setting the lock indicator to the first value.
19. The receiver of claim 12 , wherein the digital signal processor comprises:
a quantizer to quantize data in the subcarrier signals; and
a soft framer circuit to receive the quantized data from the quantizer and determine the location of the frame header.
20. The receiver of claim 12 , wherein the digital signal processor is operable to determine the location of the frame header based on estimating locations of frame headers for data frames in the one or more subcarrier signals.