engleski

Design of Good Constellations for Single-Subcarrier Intensity-Modulated Optical Systems

We address the problem of constellation design for single-subcarrier intensity-modulated direct detected optical systems. We seek to design constellations that minimize the average electrical, average optical and peak optical power for a given minimum distance between constellation points. The constellation design is formulated as a nonconvex optimization problem with nonconvexq uadratic constraints, second-order cone constraints and a convex objective function. We show that this problem can be approximated by a second-order cone programming(SOCP) problem. We propose a simple iterative procedure in which the SOCP is improved in each iteration. The new constellations are compared with the best known formats in terms of power efficiency. Our 4, 8, 16-point constellations converge to the previously known constellations. More importantly, our 32-, 64- and 128-point constellations outperform the corresponding QAM-based and face-centered cubic lattice constellations.

Direct detection; intensity modulation; optical wireless communications; lattice codes; nonconvex optimization; sphere packing

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