Study On The Characteristics And Application Of ASE In QD-SOA

Quantum dot semiconductor optical amplifier(QD-SOA),as a high-speed optical signal processing device,has the advantages of high gain,low noise coefficient and wide gain bandwidth.Aiming at the characteristics and application of amplification spontaneous emission(ASE)in QD-SOA,on the one hand,the negative influence of ASE noise is analyzed,and on the other hand,multi-wavelength conversion is realized by using ASE broadband characteristic.The main research contents are as follows:(1)According to the growth mechanism and energy level distribution of the active area of the QD-SOA device,the simulation model is established,including the calculation of the gain widening and the rate equation of the carrier.Aiming at the problem that the ASE wide spectrum is difficult to deal with,the light field propagation equation containing ASE is established by means of spectral segmentation.The stability of the model is proved by the test results of the final convergence of the ASE spectrum under different initial conditions.The ASE spectra at different resolutions can be obtained by changing the accuracy of the simulation,so the method of non-uniform spectral segmentation is proposed to improve the efficiency of the simulation.(2)The influence of ASE noise in the process of QD-SOA optical amplification is studied.The distribution of ASE spectra under different signal light power is analyzed,and the distribution characteristics of QD-SOA carriers in ground state and excitation state and the role of excitation state as "cisterns" of ground state are verified.Noise figure,as the deterioration index of the ASE noise to the amplification performance,is calculated by using the ASE spectrum.The noise figure of the QD-SOA under the same length is significantly lower than that of the material and the quantum well SOA.Through simulation research,it is shown that the noise figure can be reduced by increasing the signal light power,reducing the length of the active region and reducing the reflectivity of the end surface.Finally,the simulation experiment of OOK modulated Gaussian pulse sequence transmission proves the inhibitory effect of the increase of signal light power on ASE noise.(3)A multi-wavelength converter based on cross gain modulation towards ASE(ASE-XGM)is proposed.The scheme does not require auxiliary light and can realize the wavelength conversion of broadband.In the scheme,based on the difference of saturation between ground state and excitation state,the wavelength of signal light is set in the ground state,the wavelength of the modulated ASE light is in the excitation state.Sixteen output ASE lights with extinction ratio not less than 12.3dB can be obtained at the same time by choosing 8 beams at the center wavelength of the excitation state at 1 nm intervals.The simulation results show that the rectangular pulse has a greater extinction ratio than the first order and the third order Gaussian pulse.Reducing the injection current,increasing the pulse power and pulse width can improve the extinction ratio of the ASE light after conversion,but also increase the pulse width after conversion.Finally,it is preliminarily verified that the system can realize the high speed wavelength conversion of 200Gbit/s under the OOK signal sequence.