LDPC-Coded Generalized Frequency Division Multiplexing for Intensity-Modulated Direct-Detection Optical Systems

In this paper, a low-density parity check (LDPC) coded GFDM with high-level modulation scheme is proposed for more flexible and advanced multicarrier modulation in intensity-modulated/direct-detection (IM/DD) optical systems. Then, we experimentally demonstrate an LDPC-coded GFDM with 16-quadrature amplitude modulation (16QAM) system transmitted over 20-km standard single-mode fiber at different symbol rates to verify the applicability of the proposed scheme. Furthermore, the proposed scheme with trellis-coded 32-quadrature amplitude modulation (TC-32QAM) has also been investigated and compared with the bit error rate (BER) performance with 16QAM-modulated condition. The results indicate that TC-32QAM-modulated GFDM method has a better performance than the 16QAM-modulated case. But with LDPC coding module added, the performance of the proposed system with TC-32QAM gets worse than that with 16QAM modulation. We also experimentally compare the proposed LDPC-coded scheme and the Turbo-coded scheme in the QAM-modulated GFDM IM/DD optical system. The results show the LDPC-coded optical (LCO-) GFDM scheme has lower power penalties and better BER performance. Moreover, the proposed LCO-GFDM scheme is applied in multiband transmission by optical simulation software, and the results show that multiband LCO-GFDM scheme has a better performance than that of LCO-OFDM scheme.