Research On Receiving Performance Of Intersatellite Laser Communication Systems Based On Single-Mode Fiber Coupled Self-Homodying Detection

Satellite laser communication technology, which has been attracted considerable attention, is considered to be an effective method to establish high speed satellite communication links. Space experiments have been performed by American, Europe, Japan and so on, in which intersatellite and ground-to-satellite laser communications have been realized. In order to promote this technology to real utility, American plans to adopt laser communication technology on the 3rd generation of repeater satellites in 2015.Since DPSK/self-homodying scheme has high sensitivity, which is comparable to coherent detection, relatively simple configurations and excellent spectral efficiency in dense wavelength division multiplex,it is one of the the most promising ways to approach high speed satellite laser communication.Coupling space light into single-mode fiber is one of the key technologies in satellite laser communication systems based on self-homodying detection. In practice, laser communication terminals operate in the presence of random angular jitter, which is caused by vibration of the satellite platform, noise of the tracking detector and mechanical noise of antenna. Due to influence of the surface error of optical elements, machining error of optical systems and space environment, there are wavefront aberrations in the receiving beam. Random angular jitter and wavefront aberrations have a great impact on single-mode fiber coupling efficiency, which will deteriorate the communication performance of self-homodying laser communication systems. Moreover, since the intersatellite link is established between two satellites moving relative to each other in high speed, Doppler shift due to relative motion between satellites must be taken into account.This dissertation is concerned with the research on the receiving performance of intersatellite laser communication systems based on single-mode fiber coupled self-homodying detection. Theoretical and experimental studies on coupling space light into single-mode fiber are emphasized. The effect of Doppler shift is analyzed.First of all, the influence of random angular jitter on coupling space light into single-mode fiber is studied. In the pupil plane, the coupling model in the presence of random angular jitter is established. Based on this model, the analytical expression of the mean-coupling efficiency is derived and the best coupling conditions are deduced. The compositive influence of random angular jitter and fiber misaligned errors is analyzed. Finally, simulated experiment for influence of random angular jitter on single-mode fiber coupling efficiency is performed, which verifies the correctness of theories.The influence of wavefront aberrations on single-mode fiber coupling efficiency is studied. Orthonormal polynomials on pupil weighted by the backpropagated fiber mode are constructed. Based on orthogonal polynomials, the influence of whole wavefront aberrations are investigated and the accuracy of the Strehl Ratio approximation is evaluated. The variation rules of single-mode fiber coupling efficiency with characteristic parameters of localized wavefront aberrations are found. The situations for transmission-type and reflection-type optical antennas are discussed separately.In the presence of random angular jitter, the fade characteristics of fiber-coupled signals are investigated and the average bit error rate of intersatellite self-homodying communication systems is obtained. The influence of whole and localized wavefront aberrations on communication performance of intersatellite self-homodying communication systems is evaluated. The situations for transmission-type and reflection-type optical antennas are discussed separately.A robust self-homodying receiving method is proposed for the effect of Dopper shift. The requirements for this method are discussed. When the precise active control has to be used, the impact of frequency drifts relative to optical filter's center frequency becomes evident. Optimum bandwidths of optical filters yielding optimum performance over the entire range of frequency shifts are determined to further improve the receiver performance.This dissertation can benefit the breakthrough of the technology for coupling space light into single-mode fiber and contribute to the optimization of satellite laser communication systems based on self-homodying detection.