A method for aligning optical components comprised in an optical component assembly and optical waveguides comprised in an optical waveguide assembly according to a common optical axis and by using an adapter includes providing the optical component assembly with a first alignment structure comprising a cavity designed according to the position of the optical components within the optical component assembly; providing an adapter presenting a base surface comprising a first step structure; providing the optical waveguide assembly with a second alignment structure comprising a distinct step structure designed according to the position of the waveguides within the waveguides assembly; and positioning the optical component assembly, the optical waveguide assembly and the adapter, so that a sidewall of the cavity and the distinct step structure are put in contact with a sidewall of the first step structure.