Abstract: The method in accordance with the present invention forms grooves on one side of the waveguide element, wherein the axis of each groove is aligned with the axis of the corresponding waveguide in the waveguide element, and inserts the optical fibers into the grooves. In this way, the present invention provides a method which makes the alignment of the optical fibers with the waveguide element easier, improves the tolerance of the waveguide element to mechanical and environmental factors, and miniaturizes final products including the waveguide element.