For manufacturing a connector for optical conductors on a printed circuit board a first printed circuit board part is made and an alignment piece with one or more reference faces and with one or more alignment channels for the conductors is fixed on the first printed circuit board part. The optical conductors are put in the alignment channels and are attached in the alignment piece, whereafter the parts of the optical conductors projecting out of the alignment piece and superfluous attachment material are removed by polishing and optical contact pads are formed in the upper surface of the alignment piece. A protection cover is put on the alignment piece, which protection cover seals the reference faces and the optical contact pads from the environment, whereafter the printed circuit board is completed and finally the protection cover is removed. The protection cover comprises an upper wall adapted to cover at least the surface of the alignment piece, and edges projecting downwardly from the upper wall and determining together with the upper wall a receiving space for at least a part of the alignment piece, which edges join the sides of the alignment piece when the protection cover is placed on the alignment piece.