Research On Wavelength Conversion Between XGM And XPM Based On Quantum Dot SOA Cascade

Wavelength converters and all-optical logic gates which are realized by using the nonlinear effect of quantum dot semiconductor optical amplifier?QD-SOA?can overcome the"electronic bottleneck"in optical signal processing,and the devices based on QD-SOA play a more and more important role in optical signal processing,and show great potential in all-optical network applications,so QD-SOA has been widely concerned.Quantum dot semiconductor optical amplifier?QD-SOA?has the characteristics of high gain coefficient,ultrafast gain recovery time,low temperature sensitivity and low noise index.It shows great potential in all-optical network applications in the future.Wavelength conversion and all-optical logic gates based on the nonlinearity of QD-SOA can overcome the"electronic bottleneck"in optical signal processing.And devices based on QD-SOA are playing an increasingly important role in optical signal processing,so QD-SOA has received extensive attention.QD-SOA has made great progress since it was proposed.Currently,the most widely studied technologies are cross gain modulation?XGM?,cross phase modulation?XPM?,cross polarization modulation?CPM?and four wave mixing technology based on QD-SOA.However,the wavelength conversion based on QD-SOA-XGM has serious degradation in terms of output extinction ratio,and the wavelength conversion based on QD-SOA-XPM has low conversion efficiency.Address the existing deficiencies,in order to improve the extinction ratio and conversion efficiency of wavelength converter,based on the previous work of this research group,a simulation model of cascaded XGM and XPM wavelength converter based on QD-SOA,all-optical logic NAND gate,XOR gate and OR gate are established.The factors that affect its extinction ratio and conversion efficiency as well as Q factor and contrast ratio are analyzed in detail,and the best working parameters are obtained.The research results have potential application value for the wavelength conversion based on QD-SOA and the design of all-optical logic gate.The main contents are summarized as follows:1.This paper introduces the basic principle and structure of wavelength conversion based on QD-SOA-XGM effect and QD-SOA-XPM effect,expounds the basic theory of QD-SOA,analyzes the establishment of model and the analysis method of simulation.2.The wavelength conversion characteristics of cascaded XGM and XPM based on quantum dot SOA are studied.The factors affecting Q factor,extinction ratio and conversion efficiency are analyzed,and compared with the extinction ratio of XGM and the conversion efficiency of XPM.The results show that the extinction ratio and conversion efficiency of cascade structure are obviously higher than those of XGM and XPM.Q factor can be improved by increasing probe power and the length of active region,reduced maximum mode gain and pump power.The extinction ratio can be increased by increasing the injection current,the length of active region and the pump power,reduced the probe power.Increasing maximum mode gain and active region length,decreasing loss coefficient,pump power and pulse width can increase conversion efficiency.3.The performance of all-optical logic NAND gate based on QD-SOA cascade XGM and XPM is studied.On the basis of realizing correct completion of logical computing,the relationship between Q factor and bit error rate,extinction ratio and conversion efficiency is numerically analyzed.The high extinction ratio and conversion efficiency can be obtained by increasing the injection current and the length of the active region.Increasing pump light power will increase extinction ratio but decrease conversion efficiency.Increasing the length and the width of active region,decreasing the pulse width and the maximum mode gain can increase the Q factor and decrease the bit error rate.The contrast ratio can be increased by increasing the injection current and the maximum mode gain and decreasing the pulse width.4.The performance of all-optical logic XOR gate based on QD-SOA cascade XGM and XPM is studied.On the basis of correct logic calculation,the relationship between extinction ratio and Q factor,conversion efficiency and bit error rate is analyzed.Better Q factor,extinction ratio,contrast ratio and conversion efficiency can be obtained by changing parameters such as pump power,the length and the width of active region,maximum mode gain,loss coefficient,electronic transition time t₂₁,pulse width and injection current.5.The performance of all-optical logic OR gate based on QD-SOA cascade XGM and XPM is studied and its structure and working principle are simulated and analyzed.On the basis of correctly completing the logical output,the factors affecting the performance of extinction ratio,conversion efficiency,contrast ratio and Q factor are analyzed.The contrast ratio,Q factor extinction ratio and conversion efficiency can be improved by increasing the injection current and the width of active region and decreasing the maximum mode gain and loss coefficient.However,increasing the pump power can improve the contrast ratio and extinction ratio,but can reduce Q factor and conversion efficiency.The results are of guiding significance to the study of all-optical logic gates.