Research On Radio Over Intersatellite Optical Wireless Communication System

Nowadays,with the development of satellite communication networks and the intersatellite optical wireless communication(IsOWC)link,the satellite optical communication networks are the important part of the space-based backbone information network.Radio over fiber(ROF)has been gained a lot of research attention which can provide the transparent transport of radio frequency(RF)signals.In this thesis,we mainly consider the radio over IsOWC system which avoids the demodulation of the RF signals in the electric domain.The proposed radio over IsOWC system can reduce the complexity and cost of the equipment on the satelliteThe intensity modulated with direct detection(IM/DD)scheme is mainly employed in the radio over fiber system for its simplicity,maturity and low cost.Compared to the ROF system,the radio over IsOWC system has huge power loss for the free-space transmission and the pointing error.Meanwhile,the radio over IsOWC system needs better linearity for the transmission of multiband RF signals.So,in order to achieve better performance and satisfy the special needs,the theoretical model and system scheme for the radio over IsOWC system must get deep researches.In this thesis,we introduce the basic principle and theoretical model of the radio over IsOWC system and propose the new scheme.The system performance has been analyzed and the system parameters have been optimized to get better performance.The main research achievements of the dissertation include:1.A theoretical model is set up for the pointing error with bias error and the influence of satellite vibration on radio over IsOWC system has been analyzed.Satellite vibrations of the transmitter and receiver with bias error are considered simultaneously in the pointing loss.The closed-form expressions and the numerical results of RF gain,noise figure(NF)and spurious-free dynamic range(SFDR)are given.We also propose the low-bias technology and optimize the bias point.The outage probability for the radio over IsOWC system in the presence of pointing error is analyzed and the optimum telescope diameter to minimize the outage probability is obtained.2.A phase-modulated radio over IsOWC link with balanced coherent homodyne detection is presented.The basic principle of coherent optical communication and the theoretical model of the proposed system are presented.We also derive the exact analytical expression of signal to noise and distortion radio(SNDR)and the theoretical result of the optimal modulation index.The expressions of the RF gain,NF and SFDR are derived and the numerical results are also given for demonstration.The influence of the system parameters on the performance is investigated and the power of local oscillator(LO)optical signal should be within an appropriate range to obtain the satisfactory performance.3.A double sideband-suppressed carrier(DSB-SC)modulated radio over IsOWC link with coherent homodyne detection based on the Costas optical phase locked loop(OPLL)is presented.First,the constitution,common types and performance comparison of the OPLL are given.The theoretical model and SNDR of the proposed system are presented and the optimal modulation index is obtained according to the numerical results.The influence of extinction ratio(ER)of the electrooptical modulator on the system performance is also analyzed.The expressions and the numerical results of the RF gain,NF and SFDR are also derived.In this thesis,the influence of pointing error caused by the satellite vibration is studied and the optical antennas should be adjusted periodically during the working lifetime to reduce the bias error.For the multiband transmission,the phase modulation scheme is less susceptible to crosstalk than an intensity modulation scheme.Besides,the carrier suppression provides signal-efficient amplification for the avoidance of saturating on the optical carrier and reduces the noise contributions due to the optical carrier component.So,the carrier suppression scheme can achieve better performance than the phase modulation scheme with the same system parameters.