This paper reports simulation results for 1550 nm wavelength absorption efficiency of a superconducting NbN nanowire coupled to a single-mode Si3N4 waveguide depending on SiO2 cladding thickness. Simulation results for straight, U- and W-shaped strips show that with perfect planarization (no top cladding) the absorption coefficient per unit length is 0.031, 0.07 and 0.11 dB/µm, respectively.