A method comprises: (i) forming a first optical waveguide on a first substrate; (ii) forming a second, structurally discrete optical waveguide on a structurally discrete second substrate; (iii) assembling the second substrate or second optical waveguide with the first substrate or first optical waveguide so that the first and second optical waveguides are positioned between the first and second substrates and are relatively positioned for transferring the optical signal therebetween via optical transverse coupling; and (iv) arranging the first or second optical waveguide for transferring the optical signal therebetween via substantially adiabatic optical transverse coupling with the first and second waveguides so positioned.