The rapid and significant development of communications links between satellites has made it possible to use various applications such as relay voice, video, multimedia, etc. As a result, much research has been carried out in this field during recent years to reduce power consumption and increase transmission reliability. This reported work focuses on analysis of intersatellite links in free space, with optical links using laser sources being considered in particular. The use of several different coding schemes are discussed for use in such links: multiple pulse position modulation (MPPM); digital pulse position modulation (DPPM); Dicode pulse position modulation (Dicode PPM). Work has been carried out to compare these coding schemes in terms of error weightings and coding efficiency through showing how the PCM error rate is affected by false alarm and erasure errors for MPPM, DPPM and Dicode PPM coding 3 bits of PCM. Comparison between these coding schemes is drawn in terms of sensitivity and bandwidth efficiency.