Transmission characteristics of all-optically converted QPSK and 16QAM signals

Abstract

Various types of all-optical modulation format conversions have been proposed for realizing low latency and efficient connection of networks that have different modulation formats. All-optical PAM4 to QPSK and 16QAM modulation format conversions using an HNLF and NOLM have been demonstrated for connecting data center networks. However, there has been no study on the transmission characteristics of the converted signal over a long distance. In this study, we numerically investigate the spectral efficiency and transmission characteristics of the QPSK and 16QAM signals generated by the all-optical modulation format converters. The all-optically converted 50 Gbps class QPSK and 100 Gbps class 16QAM signals require a bandwidth of 55 GHz to maintain the EVM below 10%. We demonstrate that the converted QPSK and 16QAM signals can be transmitted up to 19,500 km and 4,000 km, respectively, in both single and 8 channels transmission by preserving the sufficient channel spacing of 62.5 GHz. Because the transmission distance of the typical inter-data-center network is shorter than 200 km, the converted signals are applicable to inter-datacenter networks. Moreover, the QPSK and 16QAM signals converted from PAM4 signals after 40 km transmission in an intra-data center network are valid for transmission in inter-data-center networks.