Abstract: A new method of using fiber Bragg gratings as the sensing elements in the measurement of temperature rises of electrical appliances is proposed in this paper. Comparing with the conventional measurement method with thermocouples, the new method can overcome problems such as electromagnetic interference, hazard of electrical leakage, etc. The characteristics and key components employed in the measuring system are analyzed and discussed. The experimental results show that the temperature rises of electrical appliances under test can be obtained quickly and accurately with the specifically designed sensors made by optical fiber Bragg gratings.
Abstract: This paper described an all-optical cesium atomic magnetometer whose measuring sensitivity achieves 0.3pT/Hz1/2. In order to achieve high measuring sensitivity, the dominant parameter, a circularly polarized pumping laser which is used to polarize the cesium atoms was well discussed. After a series of experimental tests, the relationships between the output signals based on absorptive detection with pump beam were expressed here. When the optical pumping frequency was stabilized to the center of the resonance line Fg =3→Fe=4 of the cesium D1 transition, it was found that the optimum pump beam intensity was 6 mW/cm2 for this kind of magnetometer to achieve its highest sensitivity.
Abstract: Recently, atomic magnetometers have been researched widely for its ultra high sensitivity. But the influence of pump light’s duty cycle on atomic magnetometers has been concerned little. In this paper, we described a sensitive cesium atomic magnetometer based on circular dichroism, which had the advantage of easily locking the probing laser to the necessary frequency. We experimentally investigated the amplitudes and linewidths of magnetic resonance signals at different modulated duty cycle of the pump light. The result indicated that our magnetometer achieved the highest sensitivity at the duty cycle of 30%. It’s valuable for optimizing the sensitivity of most atomic magnetometers.
Abstract: A multi-scatter propagation model based on Monte Carlo method is presented. This model can be applied to all the geometries, including coplanar or noncoplanar scenario. The mathematical description of this model is deduced. We obtain the spatial positions of photon with three Cartesian coordinates after each propagation step and the received judgment conditions. Employing a photon tracing technique, Monte Carlo simulation is performed to investigate the signal impulse response and the path loss. The results indicate that, when the off-axis angle increases, the amplitude of the impulse response decreases, while the path loss increases. In addition, it is observed that the pulse width increases with the off-axis angle.
Abstract: CCD intersection measuring is an untouched technique that used to measure the coordinates of aerial moving targets, which has been widely applied in optimal test. At present, the main problem is to improve the measuring precision, and much research has been made in system structure parameter optimization, error analysis, intersection principle improving and so on. But when using the measuring system, users are always required to be clear about the working elements of the system, which restricts its usage. In addition, the instruments are disposed and many inputs must be measured manually. As a result, precision improving becomes a difficult work. After finding out the mathematic corresponding relationship between input and output variables of measuring system based on intersection measuring principle, the paper comes up with an automatic calibration algorithm wrapping up the technical details, which makes the complicated principle transparent to users. The setup and parameter adjustment of measuring system with much less manual work has been simplified and deep advancement in precision improving becomes possible.
Abstract: A novel ameliorated construction method of low density parity check(LDPC) codes, based on the construction method of Systematically Constructed Gallager(SCG) (4,k) code, is proposed. This method, compared with the construction method of SCG(4,k) code ameliorated before, has some advantages such as saving storage space and reducing computation complexity in the hardware realization. And a novel SCG-LDPC(3969,3720) code with the same 93.7% code-rate as classic RS(255,239) code and LDPC(32640,30592) code in ITU-T G.975.1 recommendation is constructed by the proposed method. The simulation analysis results show that this novel SCG-LDPC(3969,3720) code has better error-correction performance and lower decoding complexity than those of a classic RS(255,239) code and LDPC(32640,30592) code. Therefore, the SCG-LDPC(3969,3720) code can be better suitable for high-speed optical communication systems.
Abstract: As the core device of Low-light-level imaging technology, EMCCD noise performance determines imaging results of camera system at the most extend. In this paper, noise models to EMCCD and relevant parameters of the noise sources are discussed, and the noise effect to the parameters is simulated. Based on the results of noise analysis, optimum operating areas for inverted mode and non-inverted mode are carried out, which are the theoretical foundation and references to low-light-level camera system design.
Abstract: Differential Optical Absorption Spectroscopy(DOAS) is widely used to determine concentrations of atmospheric species. This paper makes a measurement of SO2 using DOAS based on LabVIEW, and compare the concentrations retrieved by the least squares method and the way of Fourier transform filtering. Experiment results indicate that the Fourier transform filtering is superior to the least squares method for monitoring a single SO2 ingredients.
Abstract: A first-principles study of LaB6 and NdB6 has been done in order to investigate their lattice constants, cell volumes, electronic structures and optical properties. Our electronic structure calculations show that the hybridizing of the Nd-p, d bands and the B-s, p states may be the main reason that NdB6 can retain its stability under ambient conditions. The DOS at EF are 0.94 and 13.70 for LaB6 and NdB6, respectively. The corresponding electronic specific heats are also obtained. Besides, the computed static reflectivities are 0.25 and 0.74 for LaB6 and NdB6, respectively. The calculated results are in good agreement with the theoretical results, although the static reflectivity of LaB6 is not consistent with the static reflectivity given in Ref. .
Abstract: In the fiber-sensing gas detection system, characteristic of near infrared absorption spectrum of the detected gas is greatly significant. The volatilized gasoline vapor is a mixture rich in various components, of which near infrared absorption spectrum shall be determined by means of experimental measurement. In this paper, an experimental platform is constructed by analyzing absorption characteristic of liquid composition in gasoline within the range of near infrared spectrum, which achieves measurement of the volatilized gasoline vapor with different concentration. In addition, reliability of this measurement method is inspected, a comparison between features of absorption spectrograms of liquid and gas is made, and linear relation of absorbance and concentration of gasoline vapor is verified. The result shows that the experimental data is acceptable and may be used as the basis of further analysis and for design of the online detecting system of gasoline vapor concentration in the hazardous environment.