A data transmission device includes a de-interleaver configured to receive, from a host device at a first data rate, a data stream including encoded data, de-interleave the data stream into a plurality of forward error correction (FEC) data streams, and output the plurality of FEC data streams at a second data rate less than the first data rate. Each of a plurality of interleavers is configured to interleave a respective one of the plurality of FEC data streams into an intermediate data stream including first data blocks and second data blocks. An encoder module configured to generate, for each of the intermediate data streams, FEC blocks including a first parity section and a first data section, the first parity section including a first parity bit corresponding to the first data blocks and a second parity bit corresponding to the second data blocks, and the first data section including the first data blocks and the second data blocks, and output the FEC blocks at the second data rate.