Two-Stage Coded Modulation for Hurwitz Constellations in Fiber-Optical Communications

Four-dimensional signal constellations based on the checkerboard lattice D4 offer a packing gain over conventional QAM constellations per polarization. Due to the increased number of nearest neighbors such power-efficient 4D formats cannot be Gray-labeled and bit-interleaved coded modulation results in a considerable performance loss. Instead, a suited coded-modulation scheme must be tailored to t...