FRAME FORMATTING FOR HIGH RATE OPTICAL COMMUNICATIONS

• US 20120189322A1
• Filed: 01/23/2012
• Published: 07/26/2012
• Est. Priority Date: 01/22/2011
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Mo, Fan, Dave, Sameep
• Granted Patent: US 8,559,828 B2
• Time in Patent Office: Days
• US Class Current: 398/188
• CPC Class Codes: H04B 10/077 using a supervisory or additional signal
• CPC Class Codes: H04B 10/505 using external modulation
• CPC Class Codes: H04B 10/516 Details of coding or modulation
• CPC Class Codes: H04B 10/6166 Polarisation demultiplexing, tracking or alignment of orthogonal polarisation components
• CPC Class Codes: H04B 10/6971 using equalisation
• CPC Class Codes: H04L 27/2096 Arrangements for directly or externally modulating an optical carrier optical modulation H04B10/503
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits

Abstract

Methods, systems, and devices are described for formatting of data streams to be transmitted over fiber optic channels, and for processing received optical signals. A data transmission device may include a digital coding and modulation module that encodes a digital data stream, inserts unique words into the digital data stream, and modulates the encoded data stream and unique words onto optical channels for transmission over an optical fiber. A demodulation and decoding device may include a unique word identification module that identifies the unique words inserted in each optical channel stream, determines one or more characteristics of the plurality of optical channels based on the unique words, and provides the one or more characteristics to one or more other modules in the demodulator and decoding device.

Claims

1. A digital coding and modulation apparatus, comprising:

a data transport layer framer module configured to;

receive an incoming data stream; and

format the data stream into data transport frames;

a coding module coupled with the data transport layer framer module and configured to encode error correction information into the data transport frames;

a unique word insertion module coupled with the coding module and configured to insert a plurality of unique words into a data stream including the data transport frames, each of the plurality of unique words corresponding to a different optical communication channel; and

an optical transmission module coupled with the unique word insertion module and configured to modulate the data transport frames and unique words onto a plurality of optical communications channels and transmit the plurality of optical communications channels over an optical fiber, each of the plurality of unique words being modulated onto an associated optical communications channel.

2. The apparatus of claim 1, further comprising a differential encoding module coupled between the unique word insertion module and the optical transmission module and configured to differentially encode data transport frames and unique words.

3. The apparatus of claim 1, further comprising a differential encoding module coupled between the coding module and unique word insertion module and configured to differentially encode data transport frames.

4. The apparatus of claim 1, wherein the optical transmission module is configured to transmit dual-polarity QPSK optical signals over an optical fiber.

5. The apparatus of claim 4, wherein,

the plurality of optical communications channels comprise a horizontal in- phase (HI) channel, a vertical in-phase (VI) channel, a horizontal quadrature (HQ) channel, and a vertical quadrature (VQ) channel;

and

a first unique word of the plurality of unique words corresponds to the HI channel, a second unique word of the plurality of unique words corresponds to the VI channel, a third unique word of the plurality of unique words corresponds to the HQ channel, and a fourth unique word of the plurality of unique words corresponds to the VQ channel.

6. The apparatus of claim 1, wherein the unique word insertion module inserts data bits corresponding to the unique words into the data stream based on a modulation scheme of the optical transmission module.

7. The apparatus of claim 1, wherein each unique word comprises a PN code that corresponds to the optical communications channel associated with the unique word.

8. A digital decoding and demodulation apparatus, comprising:

an optical interface module configured to receive a plurality of optical signals on a plurality of optical channels from an optical fiber and output a digitized version of each optical signal;

a unique word identification module coupled with the optical interface module and configured to identify a unique word in each of the plurality of optical signals; and

a demodulator module coupled with the unique word module and configured to;

receive the digitized version of the optical signals; and

demodulate the optical signals into data transport frames using characteristics of the optical signals determined using the identified unique words, the one or more characteristics comprising an identification of one or more of the plurality of data streams and timing information between one or more of the plurality of data streams.

9. The apparatus of claim 8, further comprising:

a decoder module coupled with the demodulator module and configured to perform error correction on the data transport frames; and

a data transport layer de-framer module coupled with the decoder module and configured to receive error corrected data transport frames and output a de-framed data stream.

10. The apparatus of claim 8, wherein the demodulator module comprises a differential decoding module configured to differentially decode data transport frames and unique words.

11. The apparatus of claim 8, further comprising a differential decoding module coupled between the optical interface module and the unique word identification module and configured to differentially decode the digitized version of each optical signal.

12. The apparatus of claim 8, wherein the optical interface module is configured to receive dual-polarity QPSK optical signals over an optical fiber.

13. The apparatus of claim 12, wherein the unique word identification identifies unique words in each of a horizontal in-phase (HI), vertical in-phase (VI), horizontal quadrature (HQ) and vertical quadrature (VQ) channel.

14. The apparatus of claim 13, wherein the demodulator module uses at least a phase offset determined based on the timing information to track and correct phase for each of the HI, VI, HQ, and VQ channels.

15. The apparatus of claim 8, wherein the unique word in each of the plurality of optical signals comprises a PN code that corresponds to the associated optical signal.

16. A method comprising:

receiving an incoming encoded bit stream that is to be transmitted over a plurality of optical channels in an optical fiber communication system;

inserting a unique word into the bit stream for each optical channel onto which the encoded bit stream is to be transmitted, each optical channel corresponding to a different unique word; and

transmitting the encoded bit stream and unique words over the plurality of optical channels.

17. The method of claim 16, further comprising differentially encoding the encoded bit stream.

18. The method of claim 16, wherein transmitting the encoded bit stream comprises transmitting dual-polarity QPSK optical signals over an optical fiber.

19. The method of claim 18, wherein,

the plurality of optical communications channels comprise a horizontal in-phase (HI) channel, a vertical in-phase (VI) channel, a horizontal quadrature (HQ) channel, and a vertical quadrature (VQ) channel;

and

a first unique word of the plurality of unique words corresponds to the HI channel, a second unique word of the plurality of unique words corresponds to the VI channel, a third unique word of the plurality of unique words corresponds to the HQ channel, and a fourth unique word of the plurality of unique words corresponds to the VQ channel.

20. The method of claim 16, wherein inserting a unique word comprises inserting data bits corresponding to the unique words into the encoded bit stream based on a modulation scheme used for the transmitting of the encoded bit stream.

21. The method of claim 16, wherein the unique word for each optical channel comprises a PN code that corresponds to the optical channel.

22. A method comprising:

receiving a digitized version of a plurality of optical signals received from an optical fiber communication system, the digitized version of the plurality of optical signals including a plurality of data streams corresponding to the plurality of optical signals;

identifying a unique word in each of the data streams;

determining one or more characteristics of the data streams based on the identification of the unique words, the one or more characteristics comprising an identification of one or more of the plurality of data streams and timing information between one or more of the plurality of data streams; and

demodulating the data streams into data transport frames using characteristics of the optical signals determined using the identified unique words.

23. The method of claim 22, further comprising differentially decoding the encoded bit stream.

24. The method of claim 22, wherein receiving a digitized version of a plurality of optical signals comprises receiving dual-polarity QPSK optical signals over an optical fiber.

25. The method of claim 22, wherein the plurality of data streams comprise:

horizontal in-phase (HI) stream, a vertical in-phase (VI) stream, a horizontal quadrature (HQ) stream, and a vertical quadrature (VQ) stream.

26. The method of claim 22, wherein the unique word for each data stream comprises a PN code that corresponds to the data stream.