Study On Modulation Format Recognition In Optical Fiber Communication Systems

The modulation format recognition (MFR) technology plays an important role in the field of military and civilian communication. It has been improved greatly in wireless communication, but develops slowly in optical fiber communication systems due to static nature of fiber links. However, the next generation optical network makes it possible that MFR technology can be widely used in optical communication field. Recently, many scholars start researching on this subject. Because of the less type of modulation formats recognized at present, the scope of application is limited. So in this paper, a proper optical fiber channel model is adopted to study the recognition performance of more typical, effective, widely used and promising modulation formats.Firstly, this paper uses the Gaussian Noise (GN) model which is based on nonlinear propagation to study the recognition performance of different modulation formats for Dense Wavelength Division Multiplexing (DWDM) systems. Totally,23 modulation formats are studied in this work, including 2-dimensional optimal constellation, higher-order APSK constellation, besides the common modulation formats, such as MASK, MPSK and MQAM. Because the feature parameters of MASK, MQAM and MAPSK are not constant as the signal-to-noise-ratio (SNR) changes, we propose a method which uses the training sequence to find the threshold. The simulation results show that the method improves the probability of correct classification (Pcc) up to 91% for the region with the low SNR. Moreover, this paper obtains the Pcc of the 23 modulation formats for DWDM system with various system parameters, such as the dispersion, nonlinearity and total transmission length. We also build the model of single channel dispersion-compensated optical fiber system with OptiSystem optical simulation software, to carry out a comparative study of recognition performance of different modulation formats in same order but different types. The simulation results show that MAPSK is the optimal format which Pcc is above 99%, and 2-dimensional optimal constellation is the suboptimal one with Pcc above 93% in DWDM system. But in single channel dispersion-compensated optical fiber system,2-dimensional optimal constellation shows poor adaptability to the influence of fiber channel.