This disclosure generally relates to high-speed fiber optic networks that use light signals to transmit data over a network. The disclosed subject matter includes devices and methods relating to header subassemblies and/or optoelectronic subassemblies. In some aspects, the disclosed devices and methods may relate to a header subassembly that can include: a substrate with a substrate top and a substrate bottom; at least one optoelectronic transducer on the substrate top; at least one top electrical component on the substrate top, the electrical component can be operably coupled with the optoelectronic transducer; and at least one bottom electrical component on the substrate bottom, the bottom electrical component can be operably coupled with the optoelectronic transducer.