摘要 |
Memory requirements and processing delays associated with the applicati on of forward error correction in high speed optical transmissions are substantially reduced by mapping a forward error correction code on a row-by-row basis int o unused overhead bytes in a high bit rate signal frame. By applying the forwa rd error correction code to an entire row of the signal frame on a row by row basis, approximately one row needs to be stored at a time thereby reducing the tota l memory requirements for forward error correction processing. Using SONET as an exemplary application, approximately 1/9th of the entire SONET frame (e.g ., one of nine rows) needs to be buffered for forward error correction processing. In an illustrative embodiment, four forward error correction (FEC) blocks are provided for each row for a total of 36 FEC blocks for a frame. Each FEC blo ck comprises four bytes of correction bits for a total of 32 correction bits. These 32 correction bits are mapped to unused overhead and are used for correcting errors in one block of one row of a signal frame, wherein one block covers 1/4th of the row. Other unused overhead bytes in the row can be used to carry error detection codes for detecting multiple errors in a row to determine when forward error correction should be disabled. For example, if a single bit error correcting code is employed, then error correction can be disabled to avoid false corrections i f more than one error is detected.
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