Tan Liying

Angle-of-arrival fluctuations in moderate to strong turbulence

Based on the modified spectrum, the analytic expressions for the variance and normalized covariance of angle-of-arrival (AOA) fluctuations are presented, which are applicable to the weak and strong regimes. The experimental data of AOA fluctuations validate the new derived expressions in weak and strong regimes. The results show that the receiving aperture D, outer scale and cell scale larger than the scattering disc S contribute significantly to the AOA fluctuations, and contributions from the small-scale turbulence are negligible. For the case of 4S/D ≥ 1, the receiving aperture dominates low-pass filtering effects and the new displacement variances are in good agreement with the results from the old weak-fluctuation theory. For the case of 4S/D ≥ 1, the scattering disc dominates the low-pass filtering effects and the new displacement variances depart from the results from the old weak-fluctuation theory.

Theoretical Study of Quantum Bit Rate in Free-Space Quantum Cryptography

The quantum bit rate is an important operating parameter in free-space quantum key distribution. We introduce the measuring factor and the sifting factor, and present the expressions of the quantum bit rate based on the ideal single-photon sources and the single-photon sources with Poisson distribution. The quantum bit rate is studied in the numerical simulation for the laser links between a ground station and a satellite in a low earth orbit. The results show that it is feasible to implement quantum key distribution between a ground station and a satellite in a low earth orbit.

High order generalized permutational fractional Fourier transforms

We generalize the definition of the fractional Fourier transform (FRFT) by extending the new definition proposed by Shih. The generalized FRFT, called the high order generalized permutational fractional Fourier transform (HGPFRFT), is a generalized permutational transform. It is shown to have arbitrary natural number M periodic eigenvalues not only with respect to the order of Hermite–Gaussian functions but also to the order of the transform. This HGPFRFT will be reduced to the original FRFT proposed by Namias and Lius generalized FRFT and Shihs FRFT at the three limits with M = +∞, M = 4k (k is a natural number) and M = 4, respectively. Therefore the HGPFRFT introduces a comprehensive approach to Shihs FRFT and the original definition. Some important properties of HGPFRFT are discussed. Lastly the results of computer simulations and symbolic representations of the transform are provided.

Spatial acquisition optimization based on average acquisition time for intersatellite optical communications

An analytical expression for the prediction of the parallel processing acquisition time based on spiral scan, which is correlated with the distribution function of satellite position, size of the uncertainty area, response time of terminals, link distance and beam divergence angle, is derived for satellite optical communication in the process of acquisition. And correspondingly, the estimation of the serial processing acquisition time is also presented. These expressions allow us to optimize the performance of acquisition analytically. Then the average acquisition time is discussed as a function of link distance. The optimum acquisition mode is analyzed in term of the average acquisition time. Comparison and discussion of the two modes shows that there is an critical value of link distance, L0, which determines the optimum acquisition processing mode for optical communication systems. The results obtained here is useful in facilitating parametric estimation and optimization of acquisition system design.

The elementary theory of wavelet optical diffraction

Summary form only given. We build a new optical theory that we call wavelet optics. We then analyse several phenomenon of typical optical diffraction, the filtering in spatial domain and spatial frequency domain and an optical system of formation of images with wavelet analysis.