Optical subcarrier multiplex system with joint forward error correction coding

1. A system comprising:

a joint forward error correction (FEC) code encoder to encode an associated input signal using at least one FEC code and provide an FEC code encoded output;

a symbol mapper coupled to the joint FEC code encoder and configured to map the FEC code encoded output to a modulation format and provide a serial high symbol rate signal;

a demultiplexer coupled to the symbol mapper and configured to separate the serial high symbol rate signal into a plurality of parallel low symbol rate signals, each of the plurality of low symbol rate signals having a symbol rate lower than the serial high symbol rate signal;

a subcarrier modulator coupled to the demultiplexer and configured to modulate each of the plurality of parallel low symbol rate signals with a different subcarrier frequency to provide associated subcarrier signals;

a multiplexer coupled to the subcarrier modulator and configured to multiplex the subcarrier signals to provide a subcarrier aggregate signal; and

a modulator coupled to the multiplexer and configured to modulate an optical signal in response to the subcarrier aggregate signal to provide a subcarrier multiplexed optical signal.

2. A system according to claim 1 , wherein the joint FEC code encoder comprises:

a plurality of first FEC code encoders, each of the first FEC code encoders being configured to encode an input signal using a first FEC code and provide an associated first FEC code encoded output;

an interleaver coupled to the plurality of first FEC code encoders and configured to provide an interleaved output comprising the associated first FEC code encoded outputs; and

a second FEC code encoder coupled to the interleaver and configured to encode the interleaved output with a second FEC code to provide the FEC code encoded output.

3. A system according to claim 2 , wherein the second FEC code comprises a single parity check (SPC) code.

4. A system according to claim 2 , wherein the first FEC code comprises a low density parity check code (LDPC).

5. A system according to claim 2 , wherein the first FEC code comprises a low density parity check (LDPC) code and the second FEC code comprises a single parity check (SPC) code.

6. A system according to claim 1 , wherein the subcarrier multiplexed optical signal has a quadrature amplitude modulation (QAM) format.

7. A system according to claim 1 , the system further comprising:

a subcarrier demodulator configured to receive a signal representative of subcarrier multiplexed optical signal and provide a demodulated serial output at the high symbol rate; and

a decoder coupled to the subcarrier demodulator and configured to decode the demodulated serial output using the at least one FEC code to provide a decoded output signal representative of the associated input signal.

8. A method comprising:

encoding a data stream with at least one forward error correction (FEC) code to provide an FEC code encoded output;

mapping the FEC code encoded output to a modulation format to provide a serial high symbol rate signal;

demultiplexing the serial high symbol rate signal into a plurality of parallel low symbol rate signals, each of the plurality of low symbol rate signals having a symbol rate lower than the serial high symbol rate signal;

modulating each of the plurality of parallel low symbol rate signals with a different subcarrier frequency to provide associated subcarrier signals;

multiplexing the subcarrier signals to provide a subcarrier aggregate signal; and

modulating an optical signal in response to the subcarrier aggregate signal to provide a subcarrier multiplexed optical signal.

9. A method according to claim 8 , wherein the encoding a data stream with at least FEC code comprises:

demultiplexing the data stream into a plurality of data streams;

encoding each of the plurality of data streams using a first FEC code to provide a plurality of first FEC code encoded data streams;

interleaving the first FEC code encoded data streams to provide at least one interleaved output; and

encoding the interleaved output using a second FEC code to provide the FEC code encoded data stream.

10. A method according to claim 9 , wherein the second FEC code comprises a single parity check (SPC) code.

11. A method according to claim 9 , wherein the first FEC code comprises a low density parity check code (LDPC).

12. A method according to claim 9 , wherein the first FEC code comprises a low density parity check (LDPC) code and the second FEC code comprises a single parity check (SPC) code.

13. A method according to claim 8 , wherein the subcarrier multiplexed optical signal has a quadrature amplitude modulation (QAM) format.

14. A method according to claim 8 , the method further comprising:

demodulating a signal representative of the subcarrier multiplexed optical signal provide a demodulated serial output at the high symbol rate; and

decoding the demodulated serial output using the at least one FEC code to provide a decoded output signal representative of the associated input signal.