A process of installing optical components as precisely aligning optical axes thereof is disclosed. The process, which relates to an optical module having a signal port and/or a local port, and optical components optically coupling the ports with an active device having a built-in photodiode (PD), includes steps of (a) preparing a reference mirror that emulates a housing with a side to which the ports are attached, (b) aligning an optical axis of the auto-collimator with an optical axis of the reference mirror; (c) replacing the reference mirror with the housing; (d) aligning optical axes of the optical components with the optical axis of the auto-collimator; and (e) installing the optical components within the housing.