Patent ID: 7885494

Claim:
A package-on-package stack comprising: an upper package to: send an optical signal from a first component in the upper package through a side surface of the upper package that is perpendicular to a lower side of the upper package, and send an electrical signal from the first component in the upper package; an optical interface to: receive the optical signal from the upper package, and transmit the received optical signal, where the optical interface is located on the side surface of the upper package and an upper side of a lower package; an electrical conduit, physically separate from the optical interface, to: receive the electrical signal from the upper package, and transmit the received electrical signal; and the lower package to: receive the optical signal from the optical interface through a side surface of the lower package that is perpendicular to the upper side of the lower package, receive the electrical signal, and relay the received optical signal and the received electrical signal to a second component in the lower package.