METHOD FOR CODING DIGITAL DATA, METHOD FOR DECODING DIGITAL SIGNAL, APPARATUS FOR CODING DIGITAL DATA, APPARATUS FOR DECODING DIGITAL SIGNAL, AND INTEGRATED CIRCUIT

PROBLEM TO BE SOLVED: To provide an efficient coding and modulation system for transmission of digital data over plastic optical fibers.SOLUTION: Digital data is coded by means of a three-level coset coding. A first level applies to the digital data a binary BCH coding and performs coset partitioning by means of constellation mapping and lattice transformations. A second level applies another binary BCH coding, which may be performed selectably in accordance with a desired configuration by two BCH codes with substantially the same coding rate, operating on codewords of different sizes. A third level is uncoded. Both the second and third levels undergo mapping and lattice transformation. After an addition of the levels, a second-stage lattice transformation is performed so as to obtain a zero-mean constellation. Symbols output from such a three-level coset coder are then further modulated.