A Two-Dimensional Signal Space for Intensity-Modulated Channels

A two-dimensional signal space for intensity-modulated channels is presented. Modulation formats using this signal space are designed to minimize average and peak power for a fixed minimum distance between signal points. The uncoded, high-signal-to-noise ratio, power and spectral efficiencies are compared to those of the best known formats. The new formats are simpler than existing subcarrier formats, and are superior if the bandwidth is measured as 90% in-band power. Existing subcarrier formats are better if the bandwidth is measured as 99% in-band power.