The quality and reliability of electro-optical modules can be improved, for instance, through improved testing and burn-in of an electro-optical sub-assembly. Reliability can also be enhanced through better methods of constructing an electro-optical module. By arranging both an electrical interface and an optical interface on a sub-assembly, for instance, testing can be performed on both interfaces in a single testing process. Burning-in an electro-optical sub-assembly can also improve the reliability of the module by identifying defects. A method of forming an electro-optical module can provide improved reliability by testing and/or burning-in an electro-optical sub-assembly before assembling the module.