LAUSR

Recently, Half-Cycle Nyquist Subcarrier Modulation (HC-SCM) was proposed to achieve high spectral efficiency in intensity-modulator direct-detection optical links. This paper shows that the HC-SCM scheme has a high computational load and proposes the rational Oversampled Subcarrier Modulation (OVS-SCM) as a computational efficient alternative that, furthermore, improves the spectral efficiency. The presented experimental results show that our 256-QAM proposal allows to transmit below the hard-decision forward error correction, with a throughput of 17.8 Gb/s in a 2.5 GHz bandwidth, and a spectral efficiency of 7.2 b/s/Hz, through 20 km of single-mode optical fiber.