The invention relates to a device (100a, 100b, 100c, 100d, 100e, 100f, 100g) which is provided for coupling optical signals into at least one waveguide (10) and which has at least one electro-optical converter (28), which emits the optical signals in the direction of the axis or of the core (12) of the weaveguide (10). The problem addressed by the invention is that of further developing the device such that an active alignment of the waveguide (10) is not required. This problem is solved in that the electro-optical converter (28) is received, in particular embedded, in at least one emission-side optical sub-assembly (40), the emission-side optical sub-assembly (40) has at least one guide channel (46) for aligning the waveguide (10) in relation to the electro-optical converter (28), in particular in relation to the emission opening or active surface (30) of the electro-optical converter (28), and at least one expansion (90) provided for alignment of the waveguide (10) in relation to the guide channel (46) is allocated to the emission-side optical sub-assembly (40), in particular to the guide channel (46). The invention further relates correspondingly to a device (140a, 140b, 140c, 140d, 140e, 140f, 140g) for decoupling optical signals out of at least one waveguide (10).