“…The disadvantage of DPTM is that it requires symbol synchronization and, therefore, more circuitry and complexity than other approaches, which are outside of the scope of this paper. Table 1 and Table 2 [31,40,41,42,43,44,45,46,47,50,51] summarize the characteristics of M -bit input blocks when they are converted into symbols by OOK, PPM, DPPM, MPPM, DPIM, and DH-PIM, where Rs is the time slot rate and N0 is the energy of noise. In the case of optical communication, the influence of path loss can be ignored.…”