Research On All-optical Logic Gate Based On QD-SOA Transient Cross-phase Modulation

Due to the rapid development of the Internet in recent years,the requirement for the speed of the network system is getting higher and higher.As an alternative to optoelectronic conversion of routing node signals in optical networks,all-optical network system has attracted wide attention.All-optical logic gates based on quantumdot semiconductor optical amplifier transient cross-phase modulation have many advantages,such as low threshold current,high gain,ultra-fast gain recovery,ultra-fast transmission speed and simple structure.Therefore,in all-optical network research,alloptical logic gates based on QD-SOA transient cross-phase modulation have attracted wide attention.Based on the effect of QD-SOA Transient Cross-Phase Modulation,the characteristics of all-optical logic gates based on QD-SOA Transient Cross-Phase Modulation are studied by using refined piecewise model,three-level rate equation and optical field transmission equation,interpolation calculation and Longo-Kutta method.The main contents are as follows:1.The development of all-optical communication,the vital function of all-optical wavelength converter and all-optical logic gate in all-optical network,the working principle of all-optical logic gate based on QD-SOA-MZI structure,the principle of alloptical wavelength conversion based on QD-SOA transient cross-phase modulation and the working principle of different logic gates are introduced.2.In order to solve the complex structure problem of all optical logic NOR gate based on Mach–Zehnder interferometer,a simple architecture of single quantum dot semiconductor optical amplifier and optical filter is adopted,and an all-optical logic NOR gate based on quantum dot semiconductor optical amplifier transient cross-phase modulation is proposed.The relationship between the Q-factor and extinction ratio of NOR gate and wavelength of the clock signal,peak power of the data and the clock signal,current density,electron relaxation time from the excited state to the ground state,linewidth enhancement factor,small signal gain of the QD-SOA,bandwidth of the optical filter,and the influence of the spontaneous amplification are studied,The optimized NOR gate parameters of high extinction ratio and Q factors are obtained.3.Based on the cascade structure of QD-SOA and optical filter,a All-Zero data signal is added as control light,and NOT gate is realized by using the transient cross-phase modulation effect of QD-SOA.The effects of data signal power,control optical power,clock signal power,loss coefficient,active region length and line width enhancement factor on extinction ratio,Q factor and conversion factor are studied.The results show that the scheme is not only simpler in structure than MZI scheme,but also has higher extinction ratio,Q factor and conversion efficiency.4.The dynamic chirp characteristics of optical signals can cause unique changes in the waveforms of optical signals and affect the transmission performance in complex ways.In order to analyze this characteristic,the dynamic chirp characteristics of QDSOA are studied by solving the rate equation and the transmission equation of light.The relationship between gain recovery time and chirp is analyzed.The results show that QD-SOA has a good blue chirp characteristic,and the chirp can be reduced by decreasing the pump power,increasing the probe power and decreasing the current intensity,while the gain recovery time can be improved by increasing the blue-shift chirp properly.