Ge Wu

Design of a rectangular patch antenna with a photonic crystal substrate

Abstract Patch antennas have many advantages such as low profile, conformity to planar, etc. However, as they couple power into surface-wave modes, patch antennas have low gain and low radiation efficiency. The photonic crystal (PC), due to its frequency bandgap, can diminish the surface-wave modes significantly and thus improves the gain, radiation efficiency and directivity. In this paper, a patch antenna with a PC substrate is designed and analyzed using the software package high frequency structure simulator (HFSS). The results show that the antenna with a PC substrate has a lower return loss, a higher gain and a lower side lobe level, compared with the conventional antenna.

Study on large time-delay constant temperature control system based on TEC

Abstract This paper designes a diminutive constant temperature control system based on thermoelectric cooler (TEC). Considering that the system is a large time-delay control system, the paper proposes a new method to determine the transfer function of the controlled system which gets the transfer function by doing nonlinear fitting of the step response of the controlled system. The characteristics of system model which is established by the method are basically same as the actual constant temperature control system. This method provides a new way of thinking to the design of large time-delay control system.

On the temperature characteristics of phase measurement in homodyne fiber interferometer

Abstract Different from the traditional way of using piezoelectric (PZT) phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photocurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.

Study on the influences of system parameters on bound self-similar pulse pairs in a passively mode-locked fiber laser

Abstract This paper is devoted to research the characteristics of the bound self-similar pulses formed in a passively mode-locked Yb-doped fiber laser. The parabolic shape bound self-similar pulses with linear chirps are observed in the fiber laser. The influences of the small signal gain and the inter-cavity average group velocity dispersion (GVD) on pulse separation, pulse duration, peak power and single pulse energy of the bound self-similar pulse pairs are investigated in-depth. The simulation results contribute to the study of the stable transmission of bound state pulses.

Design of high-peak current and narrow pulse driver of laser diode

Abstract This paper presents a laser diode (LD) pulse driving circuit that can generate current pulses of amplitudes range from 6 to 30A, with pulse widths varying from 5 to 100 ns and frequencies varying from 500 Hz to 50 kHz. It is with monostabillity trigger used as pulse shaping component, with power metal-oxide-semiconductor field effect transistors (MOSFETs) as fast switches and power inverter devices, with low voltage power supply that the circuit generates high-peak pulse current. As its structure is simple and easy to understoand and realize, the circuit is of great value to be used to drive pulsed semiconductor laser.

Dissipative Solitons characteristics in passively mode-locked Yb-doped fiber laser under limitation of gain saturation energy

Abstract This paper is devoted to research the characteristics of the dissipative solitons formed in a passively mode-locked Yb-doped fiber (YDF) laser under limitation of the gain saturation energy. The parabolic shape dissipative solitons with linear chirps are observed in the fiber laser. The influences of the gain saturation energy on pulse duration, peak power and single pulse energy of the dissipative solitons are investigated in-depth.

Study on parameter optimization in a passively mode-locked Erbium-doped fiber laser

Abstract Optical soliton communication is the frontier research topic of optical fiber communication. In this paper, we study optical solitons generated by passively mode-locked Erbium-doped (Er-doped) fiber (EDF) laser. We analyze the variation of nonlinear equilibrium point parameter N of the passively mode-locked EDF laser in the role of group-velocity dispersion (GVD) and small-signal gain, and adjusting system parameter N is as close as to possible to 1. The ground state first-order optical soliton which generated through system parameter optimization of the passively mode-locked EDF laser will improve the efficiency and stability of optical soliton communication system. The research of this paper will have provided the theoretical foundation of parameter optimization in a passively mode-locked EDF laser. And it will be possible for the passively mode-locked fiber laser in optical fiber communication system to be applied from the laboratory stage to the practical application.

Influences of finite gain bandwidth on dissipative solitons in passively mode-locked Er-doped fiber laser

Abstract Dissipative solitons in the passively mode-locked fiber lasers based on the gain medium of erbium-doped (Er-doped) fiber have attracted a lot of interest in recent years. In this paper, we study the influences of finite gain bandwidth on dissipative solitons in passively mode-locked Er-doped fiber laser. We investigate the influences of the finite gain bandwidth on pulse duration, pulse peak power and single pulse energy of dissipative solitons. The results show that gain bandwidth of the gain medium has influence on dissipative soliton characteristics in passively mode-locked Er-doped fiber laser. The research in this paper has important theoretical and practical significance.

Study on the chaotic dynamics of the mode-locked fiber ring laser

Abstract In this paper, we study the chaotic dynamics of the mode-locked fiber laser by numerical simulation. The structures of the passively mode-locked fiber laser and the actively mode-locked fiber laser are studied by modeling and analysis. By appropriately adjusting the small signal gain of the optical fiber amplifier, we observe the period-doubling bifurcations and route to chaos in the passively mode-locked fiber laser based on nonlinear polarization rotation effect. Chaos in the actively mode-locked erbium-doped fiber laser is obtained by adjusting the elliptic modulus parameter of the active modulator and the intra-cavity length. Simulation results have theoretical significance for the practical application of chaotic soliton communication.

Novel jagged-shaped ultra-wideband antenna

Abstract In this article, we introduce a novel antenna with jagged-shaped patch and fed by a coplanar waveguide(CPW). This article also shows two-order optimization of patch and ground plane optimization. The size of the substrate is 30 mm× 26 mm× 0.8 mm and the substrate material uses RT5880 with relative permitivity of 2.b The simulations and experimental results demonstrate that the impedance bandwidth of antenna can be achieved from 2.2 GHz to 10 GHz. The antenna can be widely used in ultra-wideband (UWB) system.