Abstract: A testable substrate for mounting an optical component is provided with a base member having a plurality of optical component mounting areas in which light emitters and light detectors for detecting lights emitted from the light emitters are mounted, a first insulating layer formed on the base member, a second insulating layer formed on the first insulating layer, two kinds of conductive lines to be connected with opposite electrode terminals of the light emitters mounted in the respective optical component mounting areas, and two kinds of conductive lines to be connected with opposite electrode terminals of the light detectors mounted in the respective optical component mounting areas. At least one of the two kinds of conductive lines to be connected with the light emitters and at least one of the two kinds of conductive lines to be connected with the light detectors are laid on different ones of the first and second insulating layers.

Abstract: On one principal plane of a silicon substrate 1, a silicon oxide film 2 having an opening 2a is formed, and a silicon nitride film 3 having an opening 3b overlapping the opening 2a and a recessed marker 3b is stacked on the silicon oxide film 2. Next, the substrate 1 is etched through the openings 2a, 3a to provide an alignment groove 1a for an optical waveguide, and an electrode pattern 5 is formed. Light of which wavelength transmits through the substrate 1 and the silicon oxide film 2 is radiated from the other principal plane of the substrate 1, and the optical element is assembled with the marker 3b serving as the reference while the marker 3b and the optical element are monitored.