Impact And Optimization Analysis Of ADC Bandwidth And Clipping Ratio On The CDM/SCM-PON Systems

With the rapid development of optical communication technology, like high-speed backbone technology, combined with digital signal processing (DSP) technology PON is a new type of PON in the future direction of development. The new based on electrical code division multiple access and subcarrier multiplexing passive optical network (CDM/SCM-PON), which our research group proposed before, has one bright spot is that it can be integrated with the OFDM and DSP technologies. The main tasks in this paper are as follows:1.Detailed description and analysis of the basic technologies which have been applied in this CDM/SCM-PON has been given first of all. Because of the same characteristic with OFDM system CDM/SCM-PON also has high peak to average power ratio (PAPR) and the DSP technology, some important parameters of impact and optimization, including both parameters of analog-to-digital converter (ADC) bandwidth and resolution, and signal clipping ratio (CR) optimization of processing.2. In this paper, by VPI and Matlab to create a simulation system, a1Gb/s x15-bit users of CDM/SCM-PON, data modulation format selected16QAM, and selection of the dual-electrode Mach-Zehnder modulator (DE-MZM) for double sideband (DSB) modulation. Study taking into account the DSB modulation due to dispersion lead to transmission over long distances when the power attenuation, and therefore divided into two cases:no dispersion compensation and dispersion precompensation for analysis and optimization. In simulation system, choosing a second-order Gaussian low-pass filter model to simulate the impact of the ADC bandwidth, the ADC resolution as the effective number of bits (NOB), while the ADC sampling rate is fixed; clipping the electrical signal by the clipping ratio (CR); and the performance of the system to be evaluated by the error vector magnitude (EVM). Transmission fiber choice of standard single-mode fiber (SSMF), during the simulation taking into account nonlinear effects, and considerations for the uncompensated system both back to back and after40km transmission, and consider the use of dispersion pre-compensation system both back to back and after60km transmission, and the results compared. Obtained for uncompensated system, the receiving end to optimize the CR value is selected as4, and when the NOB of ADC not less than5, EVM less than0.12; for dispersion pre-compensation system, its signal clipping appropriate to add in transmitter, and CR optimize value is also4, the signal clipping technique used in transmitter before the pre-compensation part affected the optimization of the system optical modulation index (OMI), the optimal OMI value selected by the CR value, the same NOB of ADC is not less than5, the EVM less than0.12.