Research On Characteristics Of Transceiving Systems Of Inter-satellite Laser Communication Based On Acousto-optic Deflectors

Inter-satellite optical communication technology with laser as information carrier has become a current hot research areas because of its high data rate and safety. Tracking-pointing system is the key to establish optical communication link and ensure the quality of communication. Usually coarse-fine hybrid mechanism is used as tracking-pointing system. But the size, weight and power consumption of this kind of structure are difficult to reduce. Optical system coarse-fine coaxial alignment and control algorithm aiming at coordinated are both very complex. An acousto-optic deflector(AOD) with high precision, high bandwidth and large deflection range provides a new alternative for tracking-pointing system in inter-satellite optical communications.But acousto-optic deflector is a kind of dispersion device. The optical paths are not coincidence when two laser beams with different wavelengths counter-propagate an acousto-optical deflector, which will lead to transmitting and receiving beam coaxiality error. In addition, the change of incident angle of the beam into the acousto-optic deflector will cause the change of diffraction efficiency curve in ultrasonic working frequency band, when the fluctuation of transmitting and receiving light intensity will affect the quality of communication. So the research of infuence of the dispersion characteristics of an acousto-optic deflector and the incident angle of a beam on inter-satellite optical communication transceiver system features has important significance. This dissertation is organized as follows:The influence of the dispersion characteristics of an acousto-optic deflector on the transmitting and receiving beam coaxiality in inter-satellite optical communication system is studied. The optical paths are coincidence when the light beam with same wavelength counter-propagate an acousto-optical deflector is verified by an experiment. By solving Dixon equations the relationship between the deflection angle and the wavelength is obtained. We got the changing rule of transmitting and receiving beam coaxiality error with the ultrasonic frequency.The influence of incident angle in an acousto-optic deflector on transmitting and receiving light intensity in inter-satellite optical communication system is studied. The coupled wave equations of abnormal acousto-optic interaction is established under the condition of gaussian beam and the non-planar ultrasonic. The changing rule of diffraction light intensity of an acousto-optic deflector with the ultrasonic frequency is deduced under spatial-frequency domain by the method of transfer function. The effect of beam incident angle on the the light intensity fluctuation is analyzed. An experiments demonstrates the validity of the theoretical analysis.The acousto-optic deflector used under broadband matching mode in transmitting light path and under non-broadband matching mode in receiving light path is proposed to meet the both demands of large range of pointing and large field of view. According to the coaxiality error of transmitting and receiving beams caused by the dispersion characteristics of an acousto-optic deflector, a parallel AOD tracking-pointing system design is put forward. According to the diffraction intensity fluctuation of an acousto-optic deflector in ultrasonic frequency band, a method of adjusting ultrasonic power synchronously with the ultrasonic frequency to stabilize the diffraction intensity is established. The possibility of an aliasing phenomenon of diffraction beams when ultrasonic frequency is switched in high-speed is analyzed.Research work in this dissertation is aimed at providing valuable reference to practical application on the acousto-optical deflector in inter-satellite optical PAT system.