Embodiments of the present disclosure describe techniques and configurations for an enclosure that can be used for channel isolation in a multi-channel modulator driver such as, for example, an optical modulator driver. A system may include a substrate, a multi-channel modulator driver mounted on the substrate, and an enclosure mounted on the substrate to cover the multi-channel modulator driver, the enclosure having a wall that is disposed between first components of the multi-channel modulator driver associated with a first channel and second components of the multi-channel modulator driver associated with a second channel, the wall being composed of an electrically conductive material. Other embodiments may also be described and/or claimed.