This invention details how a low cost opto coupler can be made on Silicon On Insulator (SOI) using conventional integrated circuit processing methods. Specifically, metal and deposited insulating materials are use to realize a top reflector for directing light generated by a silicon PN junction diode to a silicon PN junction photo diode detector. The light generator or LED can be operated either in the avalanche mode or in the forward mode. Also, side reflectors are described as a means to contain the light to the LED-photo detector pair. Furthermore, a serpentine junction PN silicon LED is described for the avalanche mode of the silicon LED. For the forward mode, two LED structures are described in which hole and electrons combine in lightly doped regions away from heavily doped regions thereby increasing the LED conversion efficiency.