All-Optical Modulation Format Conversions from PAM4 to QPSK and 16QAM Using Silicon-Rich Nitride Waveguides

Quadrature phase -shift keying (QPSK) and 16-quadrature amplitude modulation (16QAM) formats are deployed in inter -data center networks where high transmission capacity and spectral efficiency are required. However, in intra-data center networks, a four -level pulse amplitude modulation (PAM4) format is deployed to satisfy the requirements for a simple and low-cost transceiver configuration. For the seamless and effective connection of such heterogeneous networks without an optical-electrical- optical conversion, an all -optical modulation format conversion technique is required. In this paper, we propose all -optical PAM4 to QPSK and 16QAM modulation format conversions using silicon -rich nitride waveguides. The successful conversions from 50-Gbps-class PAM4 signals to 50-Gbps-class QPSK and 100-Gbps-class 16QAM signals are demonstrated via numerical simulations.