A flex interconnect with an integrated electrical-to optical and optical-to-electrical transport layer, which enables the optical transport of critical high speed data without the need of expensive and bulky optical connectors. The flex interconnect assembly includes a flexible printed circuit substrate, which includes one or more electrical interconnects, formed on the flexible printed circuit substrate, for transmitting one or more electrical signals respectively. The flexible printed circuit substrate also includes an optical waveguide mounted onto the substrate. The optical waveguide includes an integral optical transport layer, including electrical-to-optical and optical-to-electrical interfaces connected at either end of the optical waveguide. With the integrated optical transport layer, the flex interconnect can receive electrical signals, convert and transmit them to optical signals, and then convert them back to electrical signals, all without expensive and bulky opto-electrical connectors. In one embodiment, the flex interconnect is used for transmitting both electrical and optical signals in a portable device, such as a cell phone, PDA, personal computer, and the like.