Patent ID: 8634450

Claim:
A method for coding digital data for transmission over a plastic optical fibre, the method comprising the steps of: selecting the number of bits in a second and a third portion of input digital data as a function of a desired spectral efficiency; coding input digital data by a three-level coset coding including: separating from the input digital data a first portion, the second portion and the third portion of data, each with a predetermined number of bits; coding the first portion of data with a first Bose, Chaudhuri, Hocquenghem (BCH) code in a first level; providing in a second level a second BCH code and a third BCH code, wherein the third BCH code has a codeword length lower than the codeword length of the first and the second BCH code, and the third BCH code has substantially the same coderate as the second BCH code; coding the second portion with either the second or the third BCH code in the second level; in the first level, mapping the coded first portion onto symbols of a first QPSK constellation and performing a lattice transformation of the mapped symbols so as to achieve coset partitioning, wherein the lattice transformation includes translation and scaling; in the second level, mapping the coded second portion onto symbols of a second predefined constellation using QPSK or BPSK mapping depending on whether the second or third BCH code was used and performing a lattice transformation of the mapped symbols so as to achieve coset partitioning, the lattice transformation including translation, rotation by 45 degrees and scaling of the translated constellation when the number of bits per two dimensions of the second constellation is odd; in the third level, mapping the third portion onto symbols of a third constellation over Z 2 or RZ 2 lattices, configured according to the desired spectral efficiency and performing a lattice transformation of the mapped symbols, the lattice transformation including translation, rotation of the translated constellation by 45 degrees when the number of bits per two dimensions of the configured constellation is odd, and scaling; adding the transformed symbols from the first, the second and the third level resulting in a combined constellation over Z 2 or RZ 2 ; performing a second stage lattice transformation of the combined constellation for achieving a zero-mean constellation, the second stage lattice transformation including rotation of the constellation by −45 degrees when the number of bits per two dimension of the combined constellation is odd and a modulo operation for constraining the symbols of the combined constellation to a square constellation over Z 2 or RZ 2 ; and modulating the symbols encoded with the three-level coset coding using a time-domain modulation.