Laser-induced breakdown spectroscopy (LIBS) was applied to quantitative analysis of heavy metal pollution
elements in soil. The artificial neural network (ANN) algorithm is used to the processing of the complicated spectrum
lines of soil. In this paper we developed a new algorithm using weight iteration in the artificial neural network, so as to
decrease the training epochs remarkably. The spectrum line intensity of some elements, such as Cu, Cd, Al, Fe and Si,
were obtained. The limits of detection for trace elements Cu and Cd in soil were determined to be 42 and 5ppm,
A study of gaseous sulfur dioxide detection in air by Laser Induced Breakdown Spectroscopy(LIBS) is reported. Plasmas
were formed in the sulfur dioxide gas, and three lines of sulfur at 560.61nm, 567.77nm and 565.99nm were observed.
We found that the most appropriate experimental conditions for LIBS detection on sulfur dioxide gas are: Laser Pulse
Energy =100mJ, Gate Time Delay = 2us. A further study was made in detecting sulfur dioxide gas of different
concentrations by LIBS. Finally we calculated the detection limit of sulfur dioxide gas is 330ppm.
1.5μm wavelength region is the window of optical communication. Absolute frequency references that satisfy ITU-T standards in 1.5 μm region for frequency calibration are widely needed in DWDM system. In this paper, an approach of obtaining precise frequency points which ITU-T has produced has been experimented, using an acoustic frequency shift, by calibrating Fabry-Perot etalon using double acetylene absorption lines. In the experiment, mode 1955 of F-P etalon is offset frequency-locked to acetylene absorption line P14, 195500.4023GHz, with frequency stability 108 for a 30-minute measurement. After calibrating, a series of spaced 100GHz artificial absolute frequency references in 1.5μm region are obtained.
Absolute frequency reference in 1.5-μm wavelength region is very useful for DWDM system. We have studied on producing artificial 1.5-μm wavelength region absolute frequency reference by calibrating the F-P etalon. Double acetylene absorption line calibrating technique was adopted. An experiment of calibrating the Fabry-Perot etalon using double acetylene absorption lines has been demonstrated. In the experiment, Mode 1996 of the F-P etalon was locked to acetylene absorption line 1533.4621 nm. The frequency stability of the calibrated F-P etalon was about 7×10-8. After calibrating, a series of artificial absolute frequency references in 1.5-μm wavelength region was obtained. To reduce the complexity of calibrating, a novel frequency difference measurement method was introduced.
A novel method to generate carrier-suppressed return-to-zero (CSRZ) pulses by using a sampled fiber Bragg grating (FBG) is proposed, and the transmission characteristics of the CSRZ pulses are simulated and discussed. This CSRZ pulse has a duty cycle of 50%, narrower than conventional CSRZ pulse, which is due to the filtering and shaping of FBG, and leads to increase of nonlinearity and dispersion tolerance in high-speed transmission systems. Through proper design of FBG and adoption of short pulse source, this technique provides a promising way to modify the pulse shape and consequently improve system performance.
This paper focuses on the simulative optimization of modulation format, which is CS-RZ format with appropriate spectrum filtering, in a 42.7Gb/s spectrally efficient long-haul DWDM system. It is studied that the required bandwidth of the CS-RZ signal with spectrum pruning for channel spacing of 50GHz. The power loss and crosstalk are calculation under the Gaussian filter with various order and bandwidth. The influence on the CS-RZ waveform by the filter of various order and bandwidth was also investigated. Furthermore, the Q-value of the 42.7Gb/s CS-RZ signal was simulated before and after 640km fiber link transmission with 3 order Gaussian filter of various bandwidth, which simulative test system was designed as a 42.7Gb/s DWDM system with simultaneous C+L band discrete Raman amplifier by dispersion compensation fiber (DCF) as Raman medium. As a conclusion, the optimum filter bandwidth of 42GHz is obtained for the 42.7Gb/s 50GHz spaced DWDM system. Q-value of the signal is up to 8 and remains 6.7 after transmission of 640km fiber link, with the filter of the optimum bandwidth.
Time domain ABCD matrix formalism is a useful model for analyzing the characteristics of actively modelocked fiber laser. Basing on this model and giving more consideration on the influences of optical fiber dispersion and optical fiber nonlinearity, we analyzed the laserí»s characteristics of actively modelocked fiber laser, and compared the theoretical analysis results with experimental ones.
The PMD-induced pulse broadening may cause degradation of receiver sensitivity and has negative effects on the power spectrum of received signals. The paper deals with derivation of the effects of PMD-induced pulse broadening on receiver sensitivity based on the concept of mean square pulse width. It analyzes in detail the effects of PMD on the spectrum of received power. It also discusses the scheme with which the power of a certain frequency component is extracted as a feedback control signal in a PMD compensation system.