Advanced Materials Research Vols. 760-762

Abstract: The main architecture of the next generation ROADM has its "colorless"," Directionless" and "Contentionless" characteristics. The Wavelength Selective Switch (WSS) module technology includes the microelectromechanical-systems (MEMs), Planar lightwave circuit (PLC) and liquid crystal on silicon (LCOS) based technology.

Abstract: A fourth-order low-pass continuous-time filter for a WSN transmitter is presented. The active RC filter was chosen for the high linearity, designed by using the leapfrog topology imitates the passive filter. The operation amplifier (op-amp) adopted by the filter is feed-forward operation amplifier, which could get the GBW as large as possible under the low power consumption. The cut-off frequency deviation due to the process corner, aging and temperature deviation is adjusted by an automatic frequency tuning circuit. The filter in a 0.18μm RF CMOS technology consumes 1mW from a 1V power supply. The measured results of the chip show that the bandwidth is about 1.5MHz. The voltage gain of filter is about-4.5dB with the buffer, the ripple in the pass-band is lower than 0.5 dB, and the channel rejection ratio is larger than 30dB at 4MHz.

Abstract: Considering the limitation of maneuverability and real-time performance of the common atmosphere transmission calculation software, a simulation system of atmospheric transmission attenuation effect for mid-wave infrared radiation is designed in this paper. Firstly, the atmospheric transmission attenuation effect for mid-wave infrared radiation is studied. Then an approximate model for atmospheric transmission attenuation effect for MWIR is established based on theoretical approaches and empirical formula. The process of simulation system of atmospheric transmission attenuation effect for MWIR is designed, and corresponding simulation system is implemented. Finally, the comparative experiments with MODTRAN are carried out to validate the performance of the simulation system, and experimental results show that it gives a very good agreement between the calculated results within an attitude of 3 km. In addition, this system has higher performance in real-time compared with Modtran.

Abstract: Taking matchstick head as an example, the process of energetic materials ignited by lasers were numerical simulated with the smoothed particle hydrodynamics, and the numerical results of matchstick ignition time coincide well with the experimental one.

Abstract: Fiber Bragg sensors become research focus of sensing technology, and have been widely used in many applications. This paper proposed a novel Fiber Bragg Grating sensor analyzer based on FPGA (Field Programmable Gate Array) and DSP (Digital Signal Processor) platform, which converted external parameter changes into wavelength shift in fiber Bragg gratings. The system can measure real-time temperature, strain, pressure, displacement and others through key steps including data acquisition, clutter Filtering, signal peak detection, Gaussian curve fitting and weighted wavelength calculation to carry out wavelength demodulation. Moreover, it is able to achieve fault diagnosis and positioning of the fiber link. Experimental results show that the system has advantages of low power consumption, good linearity, strong robustness, high precision and resolution on wavelength demodulation. And the system is still stable and reliable after a long test under different conditions.

Abstract: Fourth-harmonic generation of an 82MHz femtosecond Ti:sapphire laser oscillator has been demonstrated by the sequential sum-frequency mixing design with BBO crystals. Frequency quadrupling of a mode-locked Ti:sapphire laser results in maximum average power of 7mW at 82 MHz with the pulse duration of 200fs. The shortest wavelength achieved is 196.5 nm.

Abstract: In the reconstruction process of digital holograph, zero-order image has a bad impact on the quality of real image. In this paper, a new way to eliminate zero-order image in digital holography is proposed. Firstly, digital holography image is decomposed by contourlet transform, then remove the low frequency. The new digital holography image is obtained by inverse contourlet transform. Experiments show that, compared with spatial filtering, frequency domain filtering, laplacian filtering and eliminate zero-order image method based on wavelet, the new method proposed in this paper can eliminate zero-order image better, whats more, the real image is also strengthened in some way.

Abstract: Tunable diode laser absorption spectroscopy (TDLAS) is a method of using a tunable diode laser scanning one of absorption lines of trace gas, this technique has advantage of high sensitivity, fast response, multi-component and non-contact measurement. We had already developed a TDLAS sensor for monitoring natural gas leakage during the natural gas production and the process of gathering and transportation in the natural gas station, but in the practical application we found that the TDLAS sensor was influenced by visibility changes. In order to overcome this interference and improve sensor stability, we present an automatic control circuit to process photoelectric signal for eliminating interference of visibility changes. Long-term monitoring results show that the concentration of CH₄ are regular and stable during the natural gas production and transmission, therefore the application of the automatic gain circuit improved the stability of the TDLAS sensor.

Abstract: laser radar is a kind of modern active optical remote sensing device and is the outcome of the combination of the traditional radar technology and the modern laser technology. It takes laser as the light source and senses remotely the target through the radiation signal generated when the detecting laser and the target interact. This paper summarizes the structure and classification of the laser radar for the purpose of atmosphere composition detection, and also discusses the existing problems and development trends.

Abstract: Ultra-wideband wireless communication technology is brought, in the coal mine communications in this paper in order to raising the safe level of communication in coal mine. Ultra-wideband wireless communication is a system which is transmitted by the extremely narrow pulse transmission. An avalanche transistor is the core of extremely narrow pulse circuit. Narrow pulse wave form can be simulated by multisim software. Acquiring the results of simulation is the extremely narrow pulse whose pulse amplitude ranging from 10 v to dozens v and pulse width is about 3 seconds. In addition to this circuit carries on the theoretical analysis, the results is quite consistent with the simulation value in this paper.