Atmospheric effects on links limit the application of free space optical communication technology. Researches of mechanism and mitigation technologies of atmospheric effects help to decrease the bit-error-rate(BER), enhance the data rate and available distance of optical communication. The mechanism researches of atmospheric effects on free space optical communication were briefly summarized, and the various influences of atmosphere on that were described, such as intensity attenuation, optical pulse stretch, intensity scintillation, beam wander, beam spreading and phase fluctuation, etc. The existing mitigation technologies of atmospheric effects were summarized. Some technologies were described, such as large aperture receiver, multiple wavelength propagation, multiple beam propagation, partially-coherent-beam propagation, adaptive optics, etc. Lastly, future research directions were given.

DTF serial sun-photometers are used to measure aerosol optical thickness and precipitable water vapor in Hefei. Comparing with other type instruments by experiment measurement, it is obvious that the daily variation tendency is basically consistent. The errors of computed parameters between DTF sun-photometer and other devices are analyzed. The results indicate that the root-mean-square errors of measured aerosol optical thickness and precipitable water vapor are all less than 8%. Comparing precipitable water vapor measured by sun-photometer with microwave radiometer, the root-mean-square error is about 5%. Via comparison certification and error analysis, DTF sun-photometer which is used to measure aerosol optical thickness and precipitable water vapor has high reliability.

1.06 μm laser atmosphere transmission characteristics are related with weather and zone closely, because of the complexity of the aerosol particles and difficulties of real-time measurement. And it is difficult to calculate the transmission characteristics. A theoretic calculation model of 1.06 μm laser atmosphere attenuation characteristics was proposed. The theoretic calculation was combined with the real information of weather, which realized the real-time calculation of 1.06 μm laser atmosphere attenuation characteristics. The engineering calculation of laser atmosphere attenuation characteristics was simplified by the method. The attenuation coefficients of 1.06 μm laser were found at 2.5 km, 3 km, 5 km, 10 km, 12 km, 14 km, 20 km with seven kinds of visibility through the experiments, and the theoretic calculation model of laser atmosphere attenuation characteristics in Suizhong area, China, was found efficiently, which validated the feasibility of the proposed method.

Using the radio sounding data during 1998～2007, the distribution characteristics of annual and seasonal mean temperature, relative humidity of upper air of the five areas in China were analyzed for 13 heights. The results show that the trends of annual mean temperature and relative humidity of upper air of the five areas in China in daytime are similar to the trends at night as the height increasing. The annual mean temperature of the five areas drops with height up to 100 hPa, where they reach the minimum, then increase with height. The annual mean relative humidity of the five areas drops with the height. Annual mean temperature and relative humidity show obvious difference between the south and north of China. As the height increase, the trends of seasonal mean temperature and relative humidity are similar to annual mean, especially the trends of autumn.

The aerosol optical thinkness (AOT) during 2005～2010 over Beijing was investigated based on POLDER data and validated using AERONET monitoring data. The result was used to analyze the temporal variation and spatial distribution of AOT. The statistic result showed that high values were observed in southeast while low values were in northwest. The AOT decreased slowly year by year during 2005～2010. Monthly average AOT had significant differences, reaching the maximum 0.65 and the minimum 0.2 in July and November, respectively. The AOT in spring and summer was higher than that in autumn and winter, and it reached the maximum and minimum in summer and autumn respectively.

Precise measurement of O4 slant column density(SCD) is meaningful for aerosol profile retrieval. Error correcting methods of O4 SCD measured with multi axis differential optical absorption spectroscopy(MAX-DOAS) is presented. Correcting factor is calculated by comparing O4 SCD measurement result of 30° and simulation result through radiative transfer model(RTM). This factor is used to correct SCDs of each elevation angle, to remove the retrieval error caused by O4 cross section absolute error and improve the SCDs precision. The result is applied to O4 SCD measurement at Hefei, and provides a possibility for aerosol profile retrieval of next step.

Back-propagation neural network combining with laser-induced breakdown spectroscopy (LIBS) are used to calibrate and quantify the contents of Ca and Mg of different kinds of slag. The networks were trained by means of a gradient descent with momentum and adaptive learning rate back-propagation algorithm. The performance of the neural networks with different inputs is studied, so as its predictive performances to be improved, and the effect of the presence of matrix-specific information in the inputs was studied. Higher performance was obtained when the network was fed with one matrix-specific spectral window than only with the areas of selected peaks. The network fed with one matrix-specific spectral window can utilize more information of spectra, and better correct the matrix effect and line interference. The inputs of the neural networks, however, need serious consideration, since they have a good effect on the measurement reproducibility and accuracy.

Nighttime visibility meter based on digital photography is an instrument for visibility observation at night with the principle of man’s eyeballing. The visibility is acquired by the luminance information of target light source image collected by CCD, and the key technology is the accuracy of splitting target source and blackbody from the collected image. A light source image processing method based on control tags watershed segmentation approach is introduced. Experimental results show that the watershed method has a good effect on extracting the target light source luminance, and can satisfy the requirements of visibility observation at night. A good agreement has achieved through the correlation analysis to Vaisala FD12 forward scattering instrument.

To realize the automatic sun-tracking based on four-quadrant detector, the working principle of four-quadrant detector is firstly analyzed and the reason of selecting four-quadrant detector is explained. The setup based on four-quadrant detector for sun-tracking is introduced, the possibility of deviation influence, such as geometry position of the sun spot, installation position between aperture iris and four-quadrant detector is deeply investigated, the consistency between four-quadrant detector and its I－V conversion circuit is analyed, and the influence of consistency on tracking precision is evaluated. The reason and rationality of deviation existence on four-quadrant detector voltage for sun-tracking are introduced. The experiment demonstrated that the designed device based on four-quadrant detector is suitable for high-precision sun-tracking.

During the signal processing of the Raman backscattered lidar, the wavelet transform is used to reduce the noise. The setting of the threshold is the key factor in the transformation. A new method, the self-adaptive hierarchical denosing with a soft threshold is presented. Comparison of different wavelets and thresholds used in the denosing procedure are also described. Compared with the usual average method, such as detail depression method and global threshold method, the self-adaptive hierarchical denosing method can increase the SNR while with maintaining the character of the peak signal. And even when the clouds exist, the signal still can be identified without much change. The detail recognition and inverting precision are thus improved.

DSP image processing solution was used to design a set of the strip correction TV detection visualization system based on DSP’s digital image processing technology. DSP’s calculation speed is quick, it can proceed parallelly, thus it is successful to solve the antinomy between the real time examination data and the real time requisition. TMS320DM642 chip was selected as a special digital multimedia processing chip, beacuse it has rich peripheral interfaces and characteristics of the video image acquisition function, which makes the image processing module integrate the image acquisition playback and image processing function, slam the door single image acquisition card, to avoid the data transmission problems occurred in the process. After deep research of DSP system, an overall program system is proposed, realizing strip correction and video detection. Experiment result indicates it can completely satisfy the request of real-time and precision.