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Knowing the various physical mechanisms of the semiconductor optical amplifier (SOA) helps us to develop a more complete numerical model. It also enables us to simulate more realistically the static behavior of the SOA_s’ birefringence effect. This way, it allows us to study more precisely the behavior of SOA_s, and particularly the impact of the amplified spontaneous emission (ASE) or the pump and probe signals as well as the optical functions based on the non-linearity of the component. In static regime, the SOA_s possess a very low amplification threshold and a saturation power of the gain which mainly depends on the optical power injected into the active region. Beyond the optical input power, the SOA is in the saturated gain regime which gives it a nonlinear transmission behavior. Our detailed numerical model offers a set of equations and an algorithm that predict their behavior. The equations form a theoretical base from which we have coded our model in several files.cpp that the <strong>Language C++</strong> executes. It has enabled us, from the physical and geometrical parameters of the component, to recover all the relevant values ​​for a comprehensive study of SOA_s in static and dynamic regimes. In this paper, we propose to make a static characterization of the effect of the nonlinear polarization rotation by realizing a pump-probe assemblage to control the power and state of polarization at the entering of the SOA.

Tunable narrow linewidth semiconductor lasers are very attractive for a variety of applications in future communications, such as dense WDM, local oscillator tuning in coherent systems, and optical switching in local area networks. For such systems, FSK is an attractive modulation scheme since the transmitter laser frequency can be modulated through direct current modulation. The frequency modulation is due to change in the refractive index of the laser medium induced by the modulated injection current. This change is a consequence of both the temperature modulation effect (dominant at low frequency) and the active region carrier density modulation effect (dominant at high rates). The laser FM response is determined by the simultaneous action of these two effects. Continuous wavelength tuning is necessary for FSK, and also desirable for WDM applications. Recent studies have been focused on the development of wavelength tunable lasers using multielectrode distributed feedback (DFB) and distributed Bragg reflector (DBR) structures [ 11. Although the theory of such lasers i s developed, some phenomena limiting the laser ultimate performance have not yet been completely understood. One of the most important devices among multielectrode lasers is the three-electrode DBR laser (see Fig. l), which has an active Fabry-Perot section, and two passive sections, one for phase control and one with a built-corrugation for frequency control. The passives waveguides are usually made of materials with a higher bandgap than that of the active layer in order to make them transparent. Hence, there is only spontaneous and no stimulated recombination in these sections. Fig. 2. represent FM response of the three-electrode DBR laser with fixed value of I , = 40mA and I , = 21, = 50mA. When the modulation current is applied to the active region, the FM response is similar to those of a conventional laser case (amplitude modulation with frequency chirping). In contrast, when the modulation current is applied to one of the passive regions, the FM response presents a flat region for low frequencies, dips and then peaks in the vicinity of IIGHz.The FM efficiency and the bandwidth depend on the modulation current into one of the passive sections or both sections.

Problem statement: Wireless networks are characterized by a dynamic topology triggered by the nodes mobility. Thus, the wireless multi-hops connection and the channel do not have determinist behaviour such as: Interference or multiple paths. Moreover, the nodes’ invisibility makes the wireless channel difficult to detect. This wireless networks’ behaviour should be scrutinized. Approach: In our study, we mainly focus on radio propagation models by observing the evolution of the routing layer‘s performances in terms of the characteristics of the physical layer. Results: For this purpose, we first examine and then display the simulation findings of the impact of different radio propagation models on the performance of ad hoc networks. To fully understand how these various radio models influence the networks performance, we have compared the performances of several routing protocols (DSR, AODV and DSDV) for each propagation model. In order to reach credible results, we focused on the notion of nodes’ speed and the number of connections by using the well known network simulator NS-2. Conclusion: To conclude, the simulation findings are to be taken as a strong reference on the three routing protocols’ behaviour; however, it shouldn’t be considered as an exact representation of its behaviour and real environment because of several simulation constraints such as: the dimension of movement field of mobile nodes, the traffic type and the simulation timing

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