Single-chip transceiver with electronic dispersion compensation for coherent optical channels
A transceiver for fiber optic communications.
1. A method for processing communication signals in a transceiver, the method comprising:
receiving, by a transmitter host interface embodied in an integrated circuit, an input host signal;
framing, by a transmitter framer embodied in the integrated circuit, the input host signal to generate a framed host signal;
encoding, by a transmitter coder embodied in the integrated circuit, the framed host signal to generate an encoded host signal for transmission over a communication channel;
equalizing a digital input ingress signal using a bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit embodied in the integrated circuit to generate an equalized ingress signal;
framing, by a receiver framer, the equalized ingress signal to generate a framed ingress signal; and
outputting the framed ingress signal by a host interface embodied in the integrated circuit, the receiver host interface compatible with a framing protocol of the receiver framer.
2. The method of claim 1 , further comprising:
converting, by an analog-to-digital converter embodied in the integrated circuit, an analog input ingress signal to the digital input ingress signal using an approximately 0.4 pJ/conversion-step figure of merit.
3. The method of claim 1 , wherein equalizing the digital input ingress signal using the bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit comprises:
performing an automatic fiber length estimator upon startup of the transceiver and automatically programming a response of a filter based on the fiber length estimation.
4. The method of claim 1 , further comprising:
performing a feedback fine carrier recovery in a feedback fine carrier recovery circuit and
performing a feed forward fine carrier recovery in a feedback fine carrier recovery circuit to recover a carrier signal of the digital input ingress signal.
5. The method of claim 4 , wherein performing the feedback fine carrier recovery comprises operating a decision directed phase-locked loop.
6. The method of claim 5 , wherein operating the decision directed phase-locked loop comprises:
computing parallel numerically controlled oscillator outputs of the decision directed phase-locked loop in a single clock cycle.
7. The method of claim 1 , further comprising:
receiving, by an analog front end, an analog input ingress signal comprising four channels including an in-phase horizontally polarized channel, an in-phase vertically polarized channel, a quadrature horizontally polarized channel, and a quadrature vertically polarized channel;
sampling, by the analog front end, each of the four channels of the analog input ingress signal at a sampling rate greater than a symbol rate to generate the digital input ingress signal; and
providing the digital input ingress signal to the bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit.
8. The method of claim 7 , wherein sampling each of the four channels comprises:
sampling each of the four channels using separate analog-to-digital converters (ADCs) for each of the four channels, wherein each of the ADCs comprise a plurality of interleaved sub-ADCs, and wherein adjacent pairs of the sub-ADCs sample out of phase with each other and share a single buffer.
9. The method of claim 7 , further comprising:
generate, by a timing recovery circuit, a timing signal based on an output of the bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit; and
providing the timing signal to the analog front end for sampling the analog input ingress signal.
10. The method of claim 1 , further comprising:
further equalizing, by a feedforward equalizer, the equalized ingress signal by performing polarization demultiplexing and compensation for polarization mode dispersion and polarization-dependent loss.
11. A method for processing communication signals in an optical communication system, the method comprising:
receiving, by a transmitter host interface embodied in an integrated circuit, an input host signal;
framing, by a transmitter framer embodied in the integrated circuit, the input host signal to generate a framed host signal;
encoding, by a transmitter coder embodied in the integrated circuit, the framed host signal to generate an encoded host signal;
convert, by an optical front end, the encoded host signal from an electrical signal to an optical output signal for transmission over a communication channel;
receiving, by the optical front end, an optical ingress signal from the communication channel;
converting the optical ingress signal to a digital input ingress signal comprising an electrical signal;
equalizing the digital input ingress signal using a bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit embodied in the integrated circuit to generate an equalized ingress signal;
framing, by a receiver framer, the equalized ingress signal to generate a framed ingress signal; and
outputting the framed ingress signal by a host interface embodied in the integrated circuit as an electrical output signal according to a framing protocol of the receiver framer.
12. The method of claim 11 , further comprising:
converting, by an analog-to-digital converter embodied in the integrated circuit, an analog input ingress signal to the digital input ingress signal using an approximately 0.4 pJ/conversion-step figure of merit.
13. The method of claim 11 , wherein equalizing the digital input ingress signal using the bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit comprises:
performing an automatic fiber length estimator upon startup of the transceiver and automatically programming a response of a filter based on the fiber length estimation.
14. The method of claim 11 , further comprising:
performing a feedback fine carrier recovery in a feedback fine carrier recovery circuit and
performing a feed forward fine carrier recovery in a feedback fine carrier recovery circuit to recover a carrier signal of the digital input ingress signal.
15. The method of claim 14 , wherein performing the feedback fine carrier recovery comprises operating a decision directed phase-locked loop.
16. The method of claim 15 , wherein operating the decision directed phase-locked loop comprises:
computing parallel numerically controlled oscillator outputs of the decision directed phase-locked loop in a single clock cycle.
17. The method of claim 11 , wherein converting the optical ingress signal to a digital input ingress signal comprises:
converting, by the optical front end, the optical ingress signal to an analog input ingress signal, the analog input ingress signal comprising four channels including an in-phase horizontally polarized channel, an in-phase vertically polarized channel, a quadrature horizontally polarized channel, and a quadrature vertically polarized channel;
sampling, by an analog front end, each of the four channels of the analog input ingress signal at a sampling rate greater than a symbol rate to generate the digital input ingress signal; and
providing the digital input ingress signal to the bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit.
18. The method of claim 17 , wherein sampling each of the four channels comprises:
sampling each of the four channels using separate analog-to-digital converters (ADCs) for each of the four channels, wherein each of the ADCs comprise a plurality of interleaved sub-ADCs, and wherein adjacent pairs of the sub-ADCs sample out of phase with each other and share a single buffer.
19. The method of claim 18 , further comprising:
generate, by a timing recovery circuit, a timing signal based on an output of the bulk chromatic dispersion, fiber length estimation, and coarse carrier recovery circuit; and
providing the timing signal to the analog front end for sampling the analog input ingress signal.
20. The method of claim 11 , further comprising:
further equalizing, by a feedforward equalizer, the equalized ingress signal by performing polarization demultiplexing and compensation for polarization mode dispersion and polarization-dependent loss.