Free space optical communication has merged the aspects of fiber optics and the wireless communication which are the most conquered and controlled telecommunication technologies. Most of the features of free space optics (FSO) are interrelated to fiber optics but the difference between them is transmission medium, which is glass in case of fiber-optics and air/vacuum in case of FSO. In the near future, communication between LEO & GEO satellites with each other which are orbiting the Earth will be done by using inter-satellite optical wireless communication (IsOWC) systems. IsOWC systems is the most significant application of the FSO and it will be installed in the space in the near future because of its low input power, no licensing by ITU, low cost, light weight, small size of the telescopes and very high data rates as compared to the radio frequency (RF) satellite systems. In this research article, IsOWC system is designed between LEO and GEO satellites by using optisystem which is not stated in past examined research works. Inter-satellite link is established between satellites which are separated by the distance of 40,000 Km at the bit rate of 10 Gbps.