Synthesis of MSBS-32QAM in a DD-MZM Based Simplified Twin-SSB System via IM/DD

This paper proposes a method for synthesizing a multiple sideband superposed 32QAM (MSBS-32QAM) signal from a QPSK and an 8QAM using a dual drive Mach-Zehnder modulator (DD-MZM) via intensity modulation/direct detection (IM/DD). This technique doubles the electrical spectral efficiency (SE) compared to DD-MZM-based single sideband (SSB) modulation because the two sidebands carry different data. Such ability to carry two different sidebands doubles the SE compared to the typical double sideband (DSB) modulation while realizing the recovery of complex DSB signal via IM/DD. Digital signal processing (DSP) is used to separate and demodulate the QPSK and 8QAM signal from the MSBS-32QAM signal, saving the optical filters/polarizers/interleaves used in the twin-SSB scheme, thus reducing receiver complexity and cost.