In optical double-layer satellite network

the stability of network is determined by the OIOLs (Optical Inter-Orbit Links) seamless handover directly.Asynchronous handover method often results in frequent topology reconfiguration.However

synchronously centralized handover leads to cutoff of connection between two layers

and thus network operation condition gets out of control.A two-step synchronous handover scheme of MEO (Medium Earth Orbit) satellite and LEO (Low Earth Orbit) satellite constellation is proposed.Connection between LEO satellites and MEO satellites is guaranteed and topology reconstructing frequency is decreased.When orbit period of MEO satellite is integer multiple of LEO satellite

space position relation between LEO and MEO satellites is investigated.The second-order aspheric perturbation model of LEO satellite and MEO satellite constellation is built up.The orbit period ratio between MEO and LEO satellite is calculated as 3.The double-layer satellite network is designed.The laser links between the two layers in the elaborately configured LEO/MEO constellation pattern are divided into two groups based on connection and handover sequence.1/4 relative periods of the MEO satellite is considered as the handover criterion.In each 1/4 relative period

one group of inter-layer laser links switches synchronously.Research results show topology reconstructing frequency is reduced to 1/7 of link handover frequency.The average network time delay is decreased by 30ms compared with synchronously centralized handover method.