Investigation On The Effect Of Nonlinear Polarization Rotation Based On The SOA

Semiconductor optical amplifier (SOA) is one of the key components in the all-optical signal processing area for its widely applications in wavelength conversion, optical logic gates, wavelength routing and high-speed optical switch. All-optical signal processing technology based on SOA nonlinear effects, as its advantages for avoiding the "electronic bottleneck" restrictions and improving the transparency of data transmission, thus, has become research focus in the field of optical communication.In most of the transport and network applications, the sensitivity of input signal polarization state in the devices is a key factor that should be considered. Therefore, the polarization-dependent characteristics of SOA where nonlinear polarization rotation (NPR) is most concerned have attracted a lot of attention. For the continuous improvement of transmission rate, SOA-NPR effect is developed toward the ultra-fast applications.Firstly, according to the characteristic of ultrafast carrier dynamics based on the SOA-NPR model, carrier heating.(CH) and spectral hole burning (SHB) effect were introduced to the numerical equations. With the ultrashort pulse inputting into SOA, the impact of the phase change induced by the CH and SHB is worth considering. Meanwhile, the polarization dependent gain characteristics, phase characteristics and chirp characteristics were studied in view of the improved model. The result is highly accordance with that of the experiment in reference.Secondly, the polarization evolution of light in SOA is analyzed with the Poincare method and Mueller matrix method. Then we can numerically obtain the polarization azimuth and the elliptical azimuth curve of the injected optical power.. The application of elliptic azimuth curves for improving the extinction ratio of wavelength conversion based on SOA-NPR is analyzed. Furthmore, the phase difference due to the birefringence in SOA, the mode gain and so on are demonstrated to change with the injected optical power or current. Finally, based on the improved ultrafast model of SOA-NPR, the effects of the NPR on the two different modulation RZ-OOK and RZ-DPSK has obtained, then the reverse wavelength conversion can be realized.Simulation result shows that, when the input pump ligth's polarization is at the same direction with TE/TM mode, the TE/TM mode of the probe ligtht will get more gain; the variation of phase shift can divide to two region: the rapid and the slow. The CH effect play a key role in the rapid region and the CDP effect act in the slow region. The characteristic of the chirp show that: no matter what mode it is, the amplitude of red-shift chirp is greater than the blue-shift chirp. With the muller matrix analyzing the evolution of the light polarization, we can get that the phase shift between TE and TM mode increases with the injected optical power, and the phase shift can achieve 180°When the inject current increases, the phase shift increases too, and achive 45°. As the presence of ASE, the degree of polarization of light will increase. After the SOA-NPR effect, the output of the RZ-DPSK signal is 2dBdB better than the RZ-OOK signal. The reverse wavelength conversion based on the ultrafast model suffers serious effects between different modes and the Q factor is 1.276 dB.