Ordinary inter-satellite optical includes at least three optical paths for acquisition,tracking and communication,the three optical paths work simultaneously and share the received power.An optimal structure of inter-satellite optical communication terminal with single working optical path at each of working stages of acquisition and communication is introduced.A space optical switch based on frustrated total internal reflection effect is applied to switch the received laser power between the acquisition sensor and the communication sensor between the stages of acquisition and communication,this is named as power fusion which means power is transferred for shutting down unused optical path.For the stages of tracking and communication,a multiple cells sensor is used to accomplish the operation of tracking while communication,this is named as function fusion which means accomplishing multiple functions by one device to reduce the redundant optical paths.For optical communication terminal with single working path structure,the total received laser power would be detected by one sensor for each different stages of acquisition,tracking and communication,the link budget would be maximized,and this design would help to enlarge the system tolerance and reduce the acquisition time.