Research On All-optical Wavelength Converter And Logic Gate Based On QD-SOA

With the rapid development of information age,all optical network with fast transmission rate,large capacity and high communication quality has become a research hotspot nowadays.The all optical logic devices based on the quantum dot semiconductor optical amplifier?QD-SOA?has attracted wide attention in the research process of all optical network,because of its lower threshold current,low noise figure,low power consumption,higher temperature stability and ultrafast gain recovery features.In this paper,the dynamic process of QD-SOA is modeled based on the refined sectionalized model.On this basis,using the Newton method and the four order Runge-Kutta method to realize the all-optical wavelength converters and logic gates based on QD-SOA.The main contents are summarized as follows:1.The development status of optical fiber communication,the characteristics of the all-optical network and the working principle of all-optical wavelength converter based on QD-SOA-MZI and the all optical logic gate of different schemes are introduced respectively.2.The all-optical wavelength converter based on QD-SOA-MZI is discussed,and bit error rate characteristic is analyzed.The results show that the increase of the maximum modal gain and the pulse width,the bit error rate will be improved.In addition,the bit error rate first decrease and then increase when improving the input pump power.However,it is necessary to choose the appropriate maximum modal gain,the pulse width and the input pump power,we should reduce the bit error rate on the basis of ensuring higer extinction ratio.3.The all-optical XOR logic gate based on QD-SOA-MZI is implemented,and the phase difference of the probe signal through the two arms of the interferometer is studied in detail.Moreover,the relationship between the phase difference and the output optical power is also discussed.Numerical results show that the increase of the length of the active regions,maximum modal gain and input pump power leads to improvement of the phase difference.As the pump pulse width increases,the phase difference of the probe signal first increases before flatting,then decreases.When the length of the active region is 2.0mm,maximum modal gain is 3000m^-1,input pump power is 5dBm,pulse width is 1.0ps,the maximum phase difference is increased to0.3277?.In addition,the output optical power also can be improved through the increase of probe signal phase difference.4.The conversion efficiency and the phase difference of the all optical logic AND gate based on QD-SOA-MZI are discussed.The results show that the phase difference of the output probe signal can be improved by decreasing the input pulse width,the loss coefficient and increasing the transition time of electrons from excited state?ES?to the ground state?GS?,the maximum modal gain.At the same time,the conversion efficiency of all-optical logic AND gate based on QD-SOA-MZI can be raised by decreasing the pulse width,the loss coefficient,the transition time of electrons from excited state?ES?to the ground state?GS?and by increasing maximum modal gain.However,it is necessary to choose the appropriate pulse width,the transition time of electrons from excited state?ES?to the ground state?GS?and the maximum modal gain,because we should consider the Q factor on the basis of improving conversion efficiency.5.The Q factor of the all-optical logic AND gate based on QD-SOA cascade structure is studied.In addition,the Q factor and the conversion efficiency of AND gate based on different structure are compared under the same conditions.The results show that,the Q factor of all-optical logic AND gate based on QD-SOA cascade structure can be raised by decreasing the pulse width,the loss coefficient and by increasing the maximum modal gain.As the transition time of electrons from excited state?ES?to the ground state?GS?increases,the Q factor decreases first and then increases.In addition,when the pulse width and the loss coefficient are changed,the Q factor and the conversion efficiency of AND gate based on the cascade structure are higher than that of the AND gate based on the MZI structure.When the transition time is less than 0.32ps or the maximum modal gain is greater than 2300m^-1,the conversion efficiency and Q factor of AND gate based on the cascade structure are higher;when the transition time is greater than 0.32ps or the maximum modal gain is less than 2300m^-1,the conversion efficiency of AND gate based on the cascade structure is higher,at this moment,the Q factor of AND gate based on MZI structure is higher.