Multi-level phase-amplitude hybrid modulation and its transmission performance analysis+

The paper proposed a novel hybrid modulation format -16-level differential phase shift keying with binary amplitude shift keying(16DPSK-ASK), which carries 5 bits per symbol. With analyzing the characteristics of optical 16-level differential phase shift keying (16DPSK), the study analyzed 16DPSK-ASK modem methods theoretically and presented the methods in their achieving processes specifically. Based on RZ-16DPSK-ASK and CSRZ-16DPSK-ASK modulation methods, spectra and their eye diagrams following demodulator of Matlab simulation were obtained. The optimal back to back extinction ratio was derived, so that the equivalent eye opening was obtained for the amplitude tributary and phase tributary. The results showed that the 16DPSK-ASK hybrid modulation methods, as a possible new modulation format, not only have much narrower spectra with higher spectrum efficiency but also simplify the transmitter and receiver comparing with the same level modulation format. The satisfactory performance of the eye diagrams obtained after demodulation suggested that it was one of the dominant candidate modulation formats high-speed optical transmission system.