Based On QD-SOA-MZI Type All-optical Logic Gate And Decision Gate Research

With the rapid increase of data services in the Internet and communications networks,efficient,high-speed,high-capacity,intelligent switching all-optical networks have become a hot research topic.Quantum dot semiconductor optical amplifier(QD-SOA)has excellent nonlinear characteristics,such as wide gain spectrum,high saturation output power,low threshold current,low temperature sensitivity.Wavelength conversion and logic operation are becoming the key technologies in all optical networks and optical communication systems.The utilization ratio of wavelength is optimized through the reuse of wavelength.Through the realization of the wavelength routing in the digital cross connect,the blocking rate of the wavelength division multiplexing(WDM)network is further reduced,which contributes to improve the flexibility and reliability of WDM Networks.Therefore,all-optical wavelength converter,optical logic gate and optical decision system have recently attracted great deal of attention of research on all-optical wavelength converters based on QD-SOA.In this paper,the static and dynamic simulation models are established based on three-energy-state model of QD-SOA,then the simulation mode is solved by using of the Newton iterative method and the Runge Kutta method.The system of all-optical wavelength conversion based on QD-SOA-XPM is established.The effect of input pulse width,the length of the active region,loss coefficient,maximum gain mode,electron transition time on two kinds of wavelength converter and logic XOR gate,OR gate based on QD-SOA-XPM is studied.The main contents are summarized as follows:1.The research significance and the development status of all optical wavelength converter,all optical logic gates and decision gates based on QD-SOA-XPM effect are clarified.2.The principle of all optical wavelength converter based on XPM(Cross-phase modulation)effect is introduced in this paper.The conversion efficiency based on XPM effects of all-optical wavelength converter are respectively analyzed with the research of quantum dot semiconductor optical amplifier(QD-SOA)wavelength conversion.Using the three-level quantum dot semiconductor optical amplifier model,conversion efficiency based on QD-SOA-XPM effect is analyzed with the change of maximum gain mode,loss coefficient,electron transition time.The results show that,reducing the input pulse width,loss coefficient,electron transition time and increasing the length of the active region,the largest gain mode can improve the wavelength converter efficiency.The conversion efficiency of converted light in all-optical XOR gate based on QD-SOA-XPM has been improved through the optimization of these parameters and set the optimum working conditions,which verified the experimentalsimulation results.And has an important guiding significance for optical network,particularly for future development of ultra-high speed information processing and all-optical networks optical decision technology.3.The principle of logic XOR gate,OR gate based on XPM effect is introduced in this paper.In order to optimize the conversion of performance of all-optical wavelength converter and improve the quality of output signal,extinction ratio(ER)? Q factor and wavelength conversion efficiency are considered as indicators to study the conversion characteristics of wavelength converters.The influence of input signal power,pulse width,maximum gain and other factors on the extinction ratio(ER)? Q factor and conversion efficiency of all-optical wavelength converter are analyzed.The results show that,in order to obtain high conversion efficiency and improve the quality of the output signal,the two indicators of wavelength conversion,extinction ratio and Q factor should be taken into account.The quality of the output signal can be improved when appropriate input pulse width,loss coefficient,electron transition time,length of the active region,the maximum mode gain be selected.The conversion efficiency of converted light in all-optical logic XOR gate and OR gate based on QD-SOA-XPM has been improved through the optimization of these parameters and set the optimum working conditions.4.The three-energy-state model of quantum dot semiconductor optical amplifier(QD-SOA)is used to study recovery properties of active region carrier.Based on Mach Zehnder interferometer(MZI)of optical decision gate structure,the effects of various parameters including inject current,pump power and confinement factor on switch contrast are analyzed in detail.The higher the current injected,the more optimized electron occupation rate and recovery properties,which also provides favorable conditions for improving optical decision gate switching speed combined with the basic physical mechanism of QD-SOA.And the properties of contrast ratio(CR)on the performance of the switch are discussed based on MZI.The simulation results show: The recovery of the carrier concentration and the electron occupation probability are improved with injection of current in the active region.In specific confinement factor range,the Contrast Ratio and performance of optical decision gate can be optimized with appropriate increase of inject current,and better all-optical switch design parameters can be obtained.Compared with the contrast of the optical switch in the two cases with or without current injection,it can be seen that the higher contrast ratio can be obtained with increase of current injection.Therefore,it is necessary to increase the injection current of QD-SOA,which can improve the contrast ratio of the optical decision gate and improve the performance of the optical switch.