Modulation And Reception Of The Modulation Formats Which Balanced The Power Efficiency And Spectral Efficiency In Optical Communication Systems

High power efficiency and high spectral efficiency are two important criteria for the choice of the optical modulation formats. With the rapidly development of the optical unrepeatered communications, such as free-space satellite optical communications, deep-sea optical communications, people take more interests in the study of the high power-efficiency modulation formats. Additionally, With the increase of the Internet business, the requirements of system capacity are growing.So, how to achieve universal high transmission efficiency is becoming an important demand. We search for some modulation formats which have high power efficiency and high spectral efficiency simultaneously.This paper discuss the application and development of high power efficiency modulation format, mainly focus on the pulse position modulation ( PPM )and the relevant hybrid modulation formats. Based on these studies, we propose a novel Nyquist-4PPm-QPSK modulation format, which balanced the performance of power efficiency and spectrum efficiency. The performance of this modulation format is also analyzed detailedly.Firstly, in this paper, we introduce the principle of pulse position modulation format and its related hybrid modulation formats, derivate and simulate the error characteristic formulas and spectral efficiency formulas. We also analyze its advantages and disadvantages.After that, we introduce the Nyquist-filtering technology and complete the Nyquist-4PPM-QPSK modulation in a digital realization.We analyze the theoretical BER characteristics, and show the signal waveform, eye diagram, constellation and frequency spectrum. Sample position and roll off factor have a Significant effect on bit error performance of the Nyquist-4PPM-QPSK. Besides, DSP receiver algorithm is also mentioned in this chapter , such as orthogonal unbalanced compensation, clock recovery, dispersion compensation, PPM demodulation, frequency offset estimation and phase recovery.Finally, the performance of the Nyquist-4PPM-QPSK modulation format is analyzed in the single channel and WDM optical fiber links by simulating separately. Compared with the QPSK which has the same spectral efficiency, Nyquist-4PPM-QPSK has more advantages in power efficiency under the same bit error rate. The Nyquist-4PPM-QPSK back-to-back transmission experiment also verifies this conclusion.