Some implementations provide a semiconductor device that includes a first die and an optical receiver. The first die includes a back side layer having a thickness that is sufficiently thin to allow an optical signal to traverse through the back side layer. The optical receiver is configured to receive several optical signals through the back side layer of the first die. In some implementations, each optical signal originates from a corresponding optical emitter coupled to a second die. In some implementations, the back side layer is a die substrate. In some implementations, the optical signal traverses a substrate portion of the back side layer. The first die further includes an active layer. The optical receiver is part of the active layer. In some implementations, the semiconductor device includes a second die that includes an optical emitter. The second die coupled to the back side of the first die.