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Abstract: A method of on-ground simulation of optical links for free-space communications by Fourier-transform, image magnification and wavefront sampling with limited apertures was proposed. An optical simulator for free-space laser links was designed, which has the range of equivalent links distances from 160,000km to 25km. It can be used for the evaluation of communication performances of optical links in space, particularly for measuring the bit error rate under a constant transmission distance or for testing the equivalent transmission distance under a constant bit error rate. System analysis indicates that the wavefront aberrations of Fourier-transform lens have the main influence on the measurement results. But these effects can be corrected only if the RMS value of wavefront aberrations of Fourier-transform lens on the work aperture is known. Simulation experiment further shows that this method will be feasible by providing excellent optical devices and fine calibration accuracy and by overcoming the environmental disturbances. [Copyright &y& Elsevier]

• Based on a far-field asymptotic expression of diode laser beams, the collimation characteristics of a diode laser beam are investigated. • A method for designing a collimating system of a laser diode is proposed, which is confirmed by experiment. • It is shown that a circular beam spot could be obtained in the far field zone, only if the beam divergence angles have the same value in the two orthogonal directions. Based on a far-field asymptotic expression of diode laser beams, the collimation characteristics of a diode laser beam are investigated. In this paper we propose a method for designing a collimating system of a laser diode and do experiment to confirm it. It is shown that the collimated beam divergence angles in the fast- and slow-axis directions are different, if the beam sizes in the two orthogonal directions near the collimating system are the same. It is also shown that a circular beam spot could be obtained in the far field zone, only if the beam divergence angles have the same value in the two orthogonal directions, although the beam is not circularized near the collimating system. [ABSTRACT FROM AUTHOR]