Apparatus for processing otn frames utilizing an efficient forward error correction

• US 20050068995A1
• Filed: 12/10/2002
• Published: 03/31/2005
• Est. Priority Date: 01/16/2002
• Status: Active Grant

• Current Assignee: Optix Networks Limited
• Original Assignee: Optix Networks Limited
• Inventors: Moshe, Haim, Altarovici, Liviu, Lahav, Danny, Dabby, Amir
• Granted Patent: US 7,573,871 B2
• Time in Patent Office: Days
• US Class Current: 370/539
• CPC Class Codes: H04J 2203/006 Fault tolerance and recovery
• CPC Class Codes: H04J 2203/0089 Multiplexing, e.g. coding, scrambling, SONET
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04J 3/1611 Synchronous digital hierarchy [SDH] or SONET H04J3/1664 takes precedence for interactions with OTN
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27

Abstract

An apparatus and method utilizing an efficient forward error correction (FEC), targeted for processing optical transport network (CTN) signals having transmission rates in excess of 10 Gbps. The FEC uses an advanced implementation of the Bose Chaudhuri Hocquenghem (BCH) code. The use of the BCH code for the FEC improves the performance over prior art solutions for both error correction and detection.

Claims

1. An apparatus for optical transport networks (OTNs) that enables efficient OTN frames processing and improved forward error correction (FEC). the apparatus having a line interface for interfacing with an external network and a system interface for interfacing with a client, the apparatus comprising:

a. a line receive unit (LRU) connected to the line interface and receiving through the line interface network OTN frames, said LRU including a Bose-Chaudhuri-Hocquenghem (BCH) decoder for performing the FEC, said LRU capable of processing said network OTN frames into LRU processed network OTN frames; and

b. a system receive unit (SRU) connected to said LRU and the system interface, said SRU capable of optional further processing of said LRU processed network OTN frames, and capable of transmitting said further processed OTN frames through the system interface to the client.

2. The apparatus of claim 1, further comprising:

c. a system transmit unit (STU) connected to the client through the system interface, said STU capable of processing client OTN frames received through said line interface into STU processed OTN frames; and

d. a line transmit unit (LTU) having an input and an output port and including a BCH encoder, said LTU connected through said input port to said LRU and said STU, and connected through said output port to the line interface, said LTU capable of processing network and client OTN frames received respectively from said LRU and said LTU, into LTU processed OTN frames, and capable of transmitting said LTU processed OTN frames through the line interface to the network.

3. The apparatus of claim 1, where said OTN frames are transmitted at a line rate selected from the group consisting from a rate of 2.5 Gbps, 10 Gbps, and 40 Gbps.

4. The apparatus of claim 1, wherein said network OTN frames are (optionally) scrambled.

5. The apparatus of claim 1, wherein said LRU further includes:

i. a framer capable of performing at least one frame alignment on at least one of said network OTN frames;

ii. a first overhead processor capable of processing overheads of said network OTN frames; and

iii a descrambler capable of descrambling said network OTN frames.

6. The apparatus of claim 2, wherein said connection of said LTU through said input port to said LRU and said STU includes a connection through a multiplexer.

7. The apparatus of claim 2, wherein said LTU further includes:

i. a second overhead processor capable of processing overheads of said client OTN frames, and, optionally, of said LRU processed network OTN frames;

ii. a framer capable of performing at least one frame alignment on at least one of said client OTN frames, and, optionally, on at least one of said LRU processed network frames; and

iii. a scrambler capable of scrambling said LTU processed OTN frames.

8. The apparatus of claim 1, wherein the line and system interfaces include each an interface selected from the group consisting from a SFI-5 interface and a SFI-4 interface.

9. The apparatus of claim 1, wherein said BCH encoder further includes means for processing the FEC area.

10. An apparatus for optical transport networks (OTNs) that enables efficient processing of both OTN and SONET/SDH signals as well as improved forward error correction (FEC), the apparatus having a line interface for interfacing with an external network and a system interface for interfacing with a client, the apparatus comprising:

a. a line receive unit (LRU) connected to the line interface and receiving through the line interface network OTN frames, said LRU including a Bose-Chaudhuri-Hocquenghem (BCH) decoder for performing the FEC, said LRU capable of processing said network OTN frames into LRU processed network OTN frames;

b. a demapper having two ports, connected to said LRU through one of said ports and capable of demapping said LRU processed OTN frames into SONET/SDH signals; and

c. a SONET system receive unit (SONET-SRU) connected to the system interface and to said demapper through said demapper'"'"'s other said port, said SONET-SRU capable of processing SONET/SDH signals received from said LRU, and capable of sending said processed SONET/SDH signals to the client through the system interface.

11. The apparatus of claim 10, further comprising:

d. a SONET system transmit unit (SONET-STU) connected to the system interface and capable of processing SONET/SDH signals received from the client;

e. a mapper having two ports and connected through one of said ports to said SONET-STU capable of mapping SONET/SDH signals into OTN frames; and

f. a line transmit unit (LTU) having an input and an output port and including a BCH encoder, said LTU connected through said input port to said LRU and to said mapper through said other mapper'"'"'s port, and connected through said output port to the line interface, said LTU capable of processing network OTN frames received from said LRU and mapped OTN frames received from said mapper into LTU processed OTN frames, and capable of transmitting said LTU processed OTN frames through the line interface to the network.

12. The apparatus of claim 10, where said OTN frames are transmitted at a line rate selected from the group consisting from a rate of 2.5 Gbps, 10 Gbps, and 40 Gbps.

13. The apparatus of claim 10, wherein said network OTN frames are scrambled.

14. The apparatus of claim 10, wherein said LRU further includes:

i. a framer capable of performing at least one frame alignment on at least one of said network OTN frames;

ii. a first overhead processor capable of processing overheads of said network OTN frames; and

iii. a descrambler capable of descrambling said network OTN frames.

15. The apparatus of claim 11, wherein said connection of said LTU through said input port to said LRU and said mapper includes a connection through a multiplexer.

16. The apparatus of claim 10, wherein said SONET/SDH signals are selected from the group consisting from OC-48/STM-16 signals, OC-192/STM-64 signals and OC-768/STM-256 signals.

17. The apparatus of claim 11, wherein said LTU further includes:

i. a second overhead processor capable of processing overheads of said client OTN frames, and, optionally, of said LRU processed network OTN frames;

ii. a framer capable of performing at least one frame alignment on at least one of said client OTN frames, and, optionally, on at least one of said processed network OTN frames; and

iii. a scrambler capable of scrambling said LTU processed OTN frames.

18. A method for enabling effective data flow from an optical transport network (OTN) to a client, comprising the steps of:

a. receiving at least one scrambled incoming OTN frame from the network, said at least one incoming frame having overheads;

b. performing a forward error correction (FEC) on said at least one incoming frame, using a Bose-Chaudhuri-Hocquenghem (BCH) code, thereby providing at least one BCH forward corrected frame; and

c. transmitting said at least one BCH forward error corrected frame to the client.

19. The method of claim 18, wherein prior to said step of performing a forward error correction (FEC), the method further comprises the steps of:

d. performing frame alignment on said at least one scrambled incoming frame; and

e. descrambling said frame-aligned at least one scrambled incoming frame;

20. The method of claim 18, wherein prior to said step of transmitting said at least one BCH forward error corrected frame to the client, the method further comprises the steps of:

f. processing information encapsulated in said overheads,

g. building new frame overheads for said at least one BCH error corrected frame; and

h. executing scrambling of said at least one BCH error corrected frame having new overheads.

21. The method of claim 18, wherein said OTN frames are transmitted at a line rate selected from the group consisting from rates of 2.5 Gbps, 10 Gbps, and 40 Gbps.

22. A method for enabling effective data flow from a client to an optical transport network (OTN), comprising the steps of:

a. receiving at least one scrambled incoming OTN frame from the client, said at least one incoming frame having overheads;

b. processing forward error correction (FEC) data on said at least one incoming frame using a Bose-Chaudhuri-Hocquenghem (BCH) code; and

c. transmitting said at least one frame encoded as a BCH coded frame to the network.

23. The method of claim 22, wherein prior to said step of processing forward error correction (FEC) data, the method further comprises the steps of:

d. performing frame alignment on said at least one scrambled incoming frame;

e. descrambling said at least one frame-aligned scrambled incoming frame;

f. processing information encapsulated in said overheads, and

g. building new frame overheads for said at least one incoming frame,

24. The method of claim 22, wherein prior to said step of transmitting said at least one BCH forward error corrected frame to the client the method further comprises the step of executing scrambling to stabilize said at least one BCH corrected frame.

25. The method of claim 22, wherein said OTN frames are transmitted at a line rate selected from the group consisting from rates of 2.5 Gbps, 10 Gbps, and 40 Gbps.

26. The method of claim 22, wherein said step of processing FEC data includes:

i. arranging each row of said at least one OTN frame into at least one code-word;

ii. processing said at least one redundant code-word for each said at least one code-word; and

iii. integrating said at least one redundant code-word in a FEC area.

27. The method of claim 26, wherein said processing of said FEC data further includes interleaving said at least one redundant code-word.

28. A method for enabling effective data flow from a first optical transport network (OTN) to a second OTN network, comprising the steps of:

a. receiving at least one scrambled incoming OTN frame from the first network, said at least one incoming frame having overheads;

b. performing a forward error correction (FEC) on said at least one incoming frame, using a Bose-Chaudhuri-Hocquenghem (BCH) code, thereby providing at least one BCH forward corrected frame;

c. transmitting said at least one BCH forward error corrected frame to the second OTN network.

29. The method of claim 28, wherein prior to said step of performing a forward error correction, the method further comprises the steps of:

d. performing frame alignment on said at least one scrambled incoming frame; and

e. descrambling said scrambled incoming frame.

30. The method of claim 28, wherein prior to said step of transmitting said at least one BCH forward error corrected frame to the second network, the method further comprises the steps of:

f. processing information encapsulated in said overheads;

g. building new frame overheads for said at least one BCH error corrected frame;

h. processing FEC data supporting said BCH code; and

i. executing scrambling of said at least one BCH error corrected frame having new overheads.

31. The method of claim 28, wherein said OTN frames are transmitted at a line rate selected from the group consisting from rates of 2.5 Gbps, 10 Gbps, and 40 Gbps.

32. The method of claim 31, wherein said step of processing FEC data includes:

i. arranging each row of said incoming OTN frame into at least one code-word,

ii. processing said at least one redundant codeword for each of said code-word, and

iii. integrating said at least one redundant word in a FEC area.

33. The method of claim 28, wherein said processing of said FEC data further includes interleaving said at least one redundant code-word.

34. The method of claim 33, wherein the length of each said at least one code-word is at least 15,232 bits.

35. A method for processing a forward error correction (FEC) data included in a FEC area in an optical transport network (OTN) frame, the FEC area supporting a Bose-Chaudhuri-Hocquenghem (BCH) code, the method comprising the steps of:

a. arranging each row of the OTN frame into at least one code-word;

b. processing said at least one redundant code-word for each code word, using a BCH encoder; and

c. integrating said redundant code-word in the FEC area.

36. The method of claim 35, wherein said at least one code-word is a BCH code-word.

37. The method of claim 35, wherein the length of said at least one code-word is at least 15,232 bits.