查看更多>>摘要：A novel broadband pulse generator based on a Fourier domain mode-locked optoelectronic oscillator (FDMLOEO) is proposed and experimentally demonstrated. The system consists of a dual-loop self-injection-locked OEO with an on-off keying (OOK) bias-controlled Mach-Zehnder modulator (MZM) as an optical switch. By applying a square-wave voltage onto the bias port of the MZM the broadband pulses are directly generated by slicing the outputs of the FDML-OEO. The duty cycle can be easily changed by just tuning that of the square wave. Different microwave pulses with the duty cycles of 1:1, 1:10 and 1:100 are demonstrated. In particular, the tunability of the central frequency and the bandwidth of the generated signal is also displayed. Furthermore, the amplitude coherence superposition of 8 pulses is increased by & SIM;16 times and the frequency modulated pulse with different central frequencies are also demonstrated. The proposed broadband microwave signal pulse generator based on the injection-locked FDML-OEO can generate signals with large time bandwidth product (TBWP), and the linearly chirped microwave waveforms (LCMWs) are widely used in modern radar systems to achieve high-resolution detection and imaging.
查看更多>>摘要：The technologies of two-dimensional sound source localization based on diaphragm extrinsic Fabry-Perot interferometer (EFPI) fiber microphone array have been studied in this paper. The fiber microphone array consists of three EFPI. Self-calibrated intensity demodulation technology with simple structure and low cost is adopted to demodulate the sound signals. Using effective sound signal extraction technology to find the starting point and end point of sound signal, combining with time differences of arrival (TDOA) positioning technology, high-precision sound source location is successfully realized. The average positioning error of this system is no larger than 4.82%. The system has the advantages of low cost, high practicability and wide application scenarios.
查看更多>>摘要：We investigate the existence and stability of fundamental solitons in the optical superlattices with self defocusing and self-focusing nonlinearity based on the fractional Schrodinger equation. With the self-defocusing nonlinearity, fundamental solitons exist in the first gap, and the stability of solitons is in accordance with the anti-Vakhitov-Kolokolov criterion. However, for the self-focusing nonlinearity, the fundamental solitons exist in the semi-infinite gap, and the stability of solitons is in accordance with the Vakhitov-Kolokolov criterion. Moreover, the power, integral form factor, and peak value of fundamental solitons versus propagation constant, Levy index, and relative strength of superlattice are illustrated. It is necessary to mention that the soliton becomes more and more localized by decreasing the Levy index in both self-defocusing and self-focusing media. It is due to the fact that small Levy index leads to weak diffraction. It should be pointed that the solitons can also exist with alpha < 1.
NSTL
Elsevier