Methods and apparatus for sub-carrier interleaving to improve overall forward error correction

Patent metadata

Field	Value
Publication number	US-12057934-B2
Application number	US-202117403815-A
Country	US
Kind code	B2
Filing date	Aug 16, 2021
Priority date	Aug 14, 2020
Publication date	Aug 6, 2024
Grant date	Aug 6, 2024

Abstract

Consistent with the present disclosure, multiple forward error correction (FEC) encoders are provided for encoding a respective one of a plurality of data streams. A mechanism is provided to mix or interleave portions of the encoded data such that each subcarrier carries information associated with each data stream, as opposed to each subcarrier carrying information associated with only a corresponding one of the data streams. As a result, both higher SNR and low SNR optical subcarriers carry such information, such that errors occurring during transmission are distributed and not concentrated or limited to information associated with a single data stream. Accordingly, at the receive end, each FEC decoder decodes information having a similar overall error rate. By balancing the error rates across each FEC encoder/decoder pair, the overall ability to correct errors improves compared to a system in which mixing or interleaving is not carried out.

First claim

What is claimed is:

1. An apparatus, comprising:
a first forward error correction encoder operable to receive first bits and provide first encoded data based on the first bits;
a second forward error correction encoder operable to receive second bits and provided second encoded data based on the second bits;
a first distributor circuit operable to provide a first plurality of data portions indicative of the first encoded data;
a second distributor circuit operable to provide a second plurality of data portions indicative of the second encoded data;
an interleaver circuit operable to receive a first one of the first plurality of data portions and a first one of the second plurality of data portions, the interleaver circuit having an output that supplies said first one of the first plurality of data portions and said first one of the second plurality of data portions; and
a fast Fourier transform circuit operable to provide first frequency domain data based on the first one of the first plurality of data portions and second frequency domain data based on the first one of the second plurality of data portions.

2. An apparatus in accordance with claim 1 , wherein the interleaver circuit is a first interleaver circuit and the fast Fourier transform circuit is a first fast Fourier transform circuit, the apparatus further including:
a second interleaver circuit operable to receive a second one of the first plurality of data portions and a second one of the second plurality of data portions; and
a second fast Fourier transform circuit operable to provide third frequency domain data based on the second one of the first plurality of data portions and fourth frequency domain data based on the second one of the second plurality of data portions.

3. An apparatus in accordance with claim 2 , further including a multiplexer that receives inputs indicative of at least one of the first and second frequency domain data and at least one of the third and fourth frequency domain data.

4. An apparatus in accordance with claim 2 , further including:
a laser operable to provide an optical signal; and
a modulator operable to modulate the optical signal to provide a plurality of optical subcarriers, a first one of the plurality of optical subcarriers carrying first information indicative of said first one of the first plurality of data portions during a first time interval and second information indicative of said first one of the second plurality of data portions during a second time interval, and a second one of the plurality of optical subcarriers carrying third information indicative of said second one of the first plurality of data portions during the first time interval and fourth information indicative of said second one of the second plurality of data portions during the second time interval.

5. An apparatus in accordance with claim 4 , wherein each of the plurality of optical subcarriers is a Nyquist subcarrier.

6. An apparatus in accordance with claim 1 , further including:
a laser operable to provide an optical signal; and
a modulator operable to modulate the optical signal to provide a plurality of optical subcarriers, one of the plurality of optical subcarriers carrying first information indicative of said first one of the first plurality of data portions during a first time interval and second information indicative of said first one of the second plurality of data portions during a second time interval.

7. An apparatus in accordance with claim 6 , wherein each of the plurality of optical subcarriers is a Nyquist subcarrier.

8. An apparatus in accordance with claim 1 , further including circuitry operable to provide first overhead information to the first one of the first plurality of data portions and the first one of the second plurality of data portions.

9. An apparatus in accordance with claim 6 , wherein the modulator includes a Mach-Zehnder modulator.

10. An apparatus in accordance with claim 1 , further including:
a laser operable to provide an optical signal;
a splitter operable to receive the optical signal, the splitter having first and second outputs, the first output providing a first portion of the optical signal;
a modulator operable to modulate the first portion of the optical signal to provide a plurality of optical subcarriers, one of the plurality of optical subcarriers carrying first information indicative of said first one of the first plurality of data portions during a first time interval and second information indicative of said first one of the second plurality of data portions during a second time interval.

11. An apparatus, comprising:
a first carrier phase correction circuit operable to receive a first input signal and provide first phase corrected output signals;
a second carrier phase correction circuit operable to receive a second input signal and provide second phase corrected output signals;
a first de-interleave circuit operable to receive first signals indicative of the first phase corrected output signals, the first de-interleave circuit having a plurality of outputs, each of which supplying a respective one of a first plurality of data portions;
a second de-interleave circuit operable to receive second signals indicative of the second phase corrected output signals, the second de-interleave circuit having a plurality of outputs, each of which supplying a respective one of a second plurality of data portions;
a combiner circuit operable to receive one of the first plurality of data portions and one of the second plurality of data portions;
a symbols-to-bits circuit operable to receive said one of the first plurality of data portions before said one of the second plurality of data portions, the symbols to bits circuit supplying a plurality of bits; and
a forward error correction decoder operable to provide a decoded output based on the plurality of bits.

12. An apparatus in accordance with claim 11 , wherein the symbols-to-bits circuit is a first symbols-to-bits circuit, the combiner is a first combiner, said one of the first plurality of data portions is a first one of the plurality of data portions, said one of the second plurality of data portions is a second one of the plurality of data portions, the plurality of bits is a first plurality of bits, the forward error correction decoder is a first forward error correction decoder, and the decoded output is a first decoded output, the apparatus further including:
a second combiner operable to receive to receive a second one of the first plurality of data portions and a second one of the second plurality of data portions;
a second symbols-to-bits circuit operable to receive said second one of the first plurality of data portions before said second one of the second plurality of data portions, the second symbols to bits circuit supplying a second plurality of bits; and
a second forward error correction decoder operable to provide a second decoded output based on the second plurality of bits.

13. An apparatus in accordance with claim 12 , further including:
a first switch coupled to the first forward error correction decoder, the first switch being operable to selectively supply the first decoded output; and
a second switch coupled to the second forward error correction decoder, the second switch being operable to selectively supply the second decoded output.

14. An apparatus in accordance with claim 12 , wherein the first input signal is associated with a first optical subcarrier among a plurality of optical subcarriers, and the second input signal is associated with a second optical subcarrier among the plurality of optical subcarriers,

Assignees

• Infinera Corp

Inventors

• Thomson Sandy
• Amado Sofia
• Mayilavelane Aroutchelvame
• Fludger Christopher
• Pringle Scott
• Awadalla Ahmed
• Sun Han
• Chiang Ting-Kuang
• Wu Yuejian

Classifications

• H04L1/0045

  Arrangements at the receiver end · CPC title

• H04B10/6165

  Estimation of the phase of the received optical signal, phase error estimation or phase error correction · CPC title

• H04B10/2575

  Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier · CPC title

• H04B10/516

  Details of coding or modulation · CPC title

• H04J14/0298

  with sub-carrier multiplexing [SCM] · CPC title