Research On All - Optical Wavelength Converter Based On QD - SOA - XPM

With the establishment of all-optical network, all optical wavelength converter based on quantum-dot semiconductor optical amplifiers has become research hotspot because of its better temperature sensitivity, lower threshold current, higher signal processing speed and quantum efficiency.Firstly, the static and dynamic simulation models are established based on the theory model of the QD-SOA, then the simulation mode is solved by using the Newton iterative method and the Runge Kutta method. The system of all-optical wavelength conversion based on QD-SOAXPM is established. The effect of input pump power, pump pulse width, active regions and maximum mode gain on the phase difference of the probe light is introduced in detail, and their influence on Q factor and chirp is studied.1. The research on phase difference of the probe light through the two arms of the interferometer with time variation has reflected the depletion and the recovery process of carriers in the active region. The phase difference of probe light can be influenced by input pump light pulse width, the maximum modal gain, input pump power and the length of the active region. And converted optical power can be improved with the increase of maximum modal gain, input pump power, the length of the active region and pulse width.2. The various effects on converted optical chirp of all-optical wavelength converter are analyzed. The chirp of the converted light can be reduced by decreasing linewidth enhancement factor, pump power, maximum modal gain and by increasing loss coefficient, pulse width. Then the signal quality also can be improved after the conversion. The positive and negative chirp peak value of output converted light are respectively 4.90 MHz and 4.40 MHz when 0.1 for linewidth enhancement factor, 300m-1 for loss coefficient,-10 d Bm for pump power, 1000m-1 for maximum modal gain and 1.0ps for pulse width. However, another pair of value are respectively 0.70 GHz, 0.60 GHz when wavelength converter is based on XGM. This shows that little peak chirp is one of the advantages of all-optical wavelength converter based on cross phase modulation converter.3. Q factor is taken as a performance index to measure the output signal quality of all-optical wavelength converter. The results show that: with the increasing of the input pump power, Q factor increases up to the maxima 8.82 dB which appears at-12 dBm of the input pump power, and then begin to decrease. Q factor decreases with the increasing of the optical pulse width, and increases with the increasing of the maximum mode gain and the length of the active layer. On the basis of the realization of the wavelength conversion by optimizing the best parameter value, the value of Q factor reaching 16.68 dB is obtained, and the output signal quality is high. In order to obtain the high extinction ratio and Q factor at the same time to improve the quality of the output converted optical signal, the appropriate input pump power must be selected for the optical power, pulse width, maximum mode gain, and length of the active layer.4. The Q factor characteristics of XPM type and XGM type wavelength converter are compared under the same conditions. Q factor can be influenced by input pump power, pulse width, the maximum mode gain and the length of active region in two different kinds of all optical wavelength converters. And the characteristics of Q factor based on cross phase modulation are better than that one. Under the condition of higher output conversion optical signal quality, require less active region length and pulse width are required by all optical wavelength converter based on cross-phase modulation effect. In addition, the pump power can change a wider range.