We have investigated the dependence of neighboring mask interference on growth pressure in narrow-stripe selective MOVPE with arrayed stripe masks for the growth of densely-arrayed optical waveguides. Atmospheric-pressure MOVPE is effective in fabricating densely arrayed waveguide without inducing neighboring mask interference. On the other hand, low-pressure MOVPE has the advantage that the distribution of PL-wavelength over the microarray waveguide can easily be controlled by utilizing neighboring mask interference. An appropriate mask pattern and growth conditions for fabricating integrated photonic devices can thus be selected. A mask interference constant was introduced and used to simulate distributions of PL-wavelengths in arrayed waveguide. Simulated results matched experimental results well,