Study of a novel amplitude-phase modulation IRZ-MSK in high-speed optical fiber transmission system

• A novel amplitude-phase modulation format, IRZ-MSK is proposed.
• A scheme to realize the IRZ-MSK is presented.
• The influence of the duty cycle on the dispersion and nonlinear tolerance of the IRZ-MSK is studied.
• The comparison between 70% IRZ-MSK and the NRZ-MSK is simulated and analyzed.
• The IRZ-MSK can greatly improve transmission performance and the spectral efficiency.

In this paper, a novel amplitude-phase modulation format, inverse-return-to-zero minimum shift keying (IRZ-MSK), is proposed. A scheme to realize the IRZ-MSK is introduced, and especially a method of demodulating the phase branch is presented. The influence of different duty cycles on the performance of the IRZ-MSK is discussed. Numerical simulations and analysis are performed, and the comparison between the 70% IRZ-MSK and the NRZ-MSK is made. The phase branches of 70% IRZ-MSK and the NRZ-MSK almost have the same dispersion tolerance, and the amplitude branch of 70% IRZ-MSK has a better dispersion tolerance than that of the NRZ-MSK when the residual dispersion is larger than 1.9 ps/nm/km. For the nonlinear tolerance, the EOP of the IRZ-MSK phase branch and amplitude branch reduces 0.5 dB and 3.8 dB than those of the NRZ-MSK respectively, when the launch power is 4 mW and dispersion is completely compensated. Meanwhile, the BER curves of the NRZ-MSK and IRZ-MSK are also made. The results show that, our proposed IRZ-MSK can not only improve the spectral efficiency, but also greatly mitigate the dispersion and nonlinear effects.