Research On The All - Optical Wavelength Conversion Characteristics Of QD - SOA Based On XGM

With the rapid increasing of demand for various data services in the internet and communication network, we have entered the era of big data, such as cloud computation serves, networking and so on. The trend of the next-generation communications network is an efficient, high-speed, high-capacity, intelligence exchange all-optical network. The wavelength conversion is one of the key technologies, which can improve wavelength utilization, reduce network congestion and achieve different protocol conversion and transparent transmission in all optical communication. Quantum dots(QDs) have recently attracting a great deal of attention in various devices such as amplifiers, lasers and detectors due to their low threshold current, lower temperature sensitivity, high differential gain and broad modulation band width. The cross-gain optical wavelength conversion is very simple to realize and has shown impressive characteristics in the quantum-dot semiconductor optical amplifier(QD-SOA). The characteristics of the all optical wavelength conversion in QD-SOA have been investigated extensively. The double-port-coupled wavelength converter based on QD-SOA has shown serious exists extinction ratio(ER) degradation,difficult fabrication,high spontaneous emission noise. A single-port-coupled wavelength converter based on cross-gain modulation(XGM) in QD-SOA is proposed.Based on the XGM of the all optical wavelength conversion in QD-SOA, the static and dynamic model is introduced. The output properties of the double-port-coupled optical wavelength converter based on QD-SOA, such as gain recovery time(GRT), extinction ratio, chirp, are analyzed in detail. The effects of various parameters, including injection current, pump power, probe power, device length, wavelength conversion span and rear facet reflectivity on the ER of the single-port-coupled QD-SOA, are calculated. Compared the ER of the single-port-coupled QD-SOA with the double-port-coupled QD-SOA, the calculated results show that the former values of ER are larger thus the single scheme has the better extinction ratio character than the double scheme. The main contents are given as following:1. The signification of all optical wavelength technology for all optical communication is introduced. The general situation about all optical wavelength technology is analyzed. A single-port-coupled wavelength conversion based on XGM in QD-SOA is proposed.2. Based on the principle of QD-SOA, the static and dynamic model is established, and the Newton method and the forth-order Runge-Kutta method are introduced. The single-port- and doubled-port-coupled QD-SOA is studied in detail. For two schemes, the gain and carrier distribution are analyzed respectively.3. Based on the XGM of QD-SOA, the double-port-coupled optical wavelength converter is achieved. The rate equations and light field transfer equations are solved by utilizing the Newton method and the forth-order Runge-Kutta method. The output properties of the double-port-coupled optical wavelength converter based on QD-SOA, such as GRT, ER, chirp, are analyzed in detail.(1) The ultra-fast gain dynamics and gain recovery time based on XGM are studied. The simulation results show that the recovery process could be accelerated by increasing the injection current, the probe power and active-region length, by decreasing the cross-sectional area and raising the holding beam power, which provides the instruction on the application in the ultra-fast optical wavelength conversion.(2) The ER of the converted signal is discussed by changing the inherent parameters and the external ones. The calculated results show that the value of ER in double-port-coupled QD-SOA can be increased by increasing the injection current, the pump power, the device length, and also be increased by decreasing the wavelength conversion span and the probe power.(3) The converted signal chirp of the double-port-coupled QD-SOA is analyzed in detail. The calculated results show that the converted signal chirp can be decreased by decreasing the injection current, the signal extinction ratio, the linewidth enhancement factor and the pump power, and also be decreased by increasing the signal pulse width and the probe power. In addition, the chirp value is robust to the signal wavelength. The low chirp of the converted signal can be achieved by optimizing these parameters.4. The effects of various parameters, including injection current, pump power, probe power, device length, wavelength conversion span and rear facet reflectivity on the extinction ratio of the single-port-coupled QD-SOA, are analyzed in detail. The results show that the converted signal extinction ratio is increased by raising the pump power, reducing the probe power, decreasing the wavelength conversion span, and increasing the injection current and device length. In addition, for the low probe power, the value of ER is increased by increasing the rear facet reflectivity. The converted signal ER decreases as the rear facet reflectivity increases for the high probe power. Compared the ER of the single-port-coupled QD-SOA with the double-port-coupled QD-SOA, the calculated results show the former values of ER are larger thus the single scheme has the better extinction ratio character than the double scheme. In addition, the single-port-coupled QD-SOA operation performance is improved due to simple implementation and large input power dynamic range as compared to the double-port-coupled QD-SOA.