OPTICAL MODULE

There is provided an optical module in which leaked light or the like from a plurality of optical elements on the same substrate is made less likely to affect adjacent optical elements, and a cross-talk noise can be thereby significantly reduced. The optical module includes an internal waveguide in a first trench of a substrate, a mirror section, and optical elements. A plurality of the first trenches of the substrate are formed independently of each other and substantially in parallel with each other, and lengths of adjacent first trenches from the end surface of the substrate are made different from each other. The optical elements are mounted on the surface of the substrate so as to oppose the minor sections formed at the tip portions of the first trenches having the different lengths.