Real-Time Demonstration of 1024-QAM OFDM Transmitter in Short-Reach IMDD Systems

In this letter, a net data rate of 5.55-Gb/s real-time baseband 1024-quadratic-amplitude modulation-encoded orthogonal frequency division multiplexing (OFDM) transmitter with an electrical spectral efficiency (SE) up to 8.88 b/s/Hz is successfully implemented on a single-field programmable gate array chip incorporating with a 2.5 GS/s 14-b digital-to-analog converter. The transmission performance is investigated in simple intensity-modulated and direct-detection, standard single-mode fiber (SSMF), and end-to-end optical communication systems. The experimental results show that the real-time optical OFDM signal with an optical SE of 3.95 b/s/Hz can be successfully transmitted over 20-km SSMF with an bit error rate below the soft-decision forward error correction threshold of , and there is a negligible power penalty compared with the optical back-to-back.