A M-Continuous-Polarization Modulation scheme for improving the bandwidth efficiency

In Multilevel Polarization Modulation (MPM), the abrupt switching among the discrete Sates of Polarization (SOPs) brings discontinuity of signal waveforms, which will broaden bandwidth and decrease the bandwidth efficiency consequently. To alleviate the problem, in this paper a Multilevel Continuous Polarization Modulation (MCPM) scheme is proposed with continuous SOP to produce continuous signal waveforms. The signal is modulated at the transmitter with continuous SOPs by changing the amplitude ratio smoothly while keeping the phase difference constant, which are two basic elements of a SOP. At the receiver, the signal is demodulated based on the change of the amplitude ratio between the current and the former received SOP, which is extracted by the Stokes receiver. Furthermore, we evaluate the scheme with bandwidth efficiency and Symbol Error Rate (SER) of the received signal in an AWGN channel. The theoretical analysis and simulation results show that when the fraction of the received signal power is 99%, the bandwidth efficiency of the MCPM is 21.87% better than the MPM. The MCPM, meanwhile, has about a 0.6dB lower requirement in per bit energy-to-noise ratio than the MPM at the same modulation order.