Micro/nano optoelectronic devices are widely studied as basic building blocks for on-chip integrated microsystem and multichannel logic units with excellent optoelectronic properties that are especially important part for interconnection route construction. Here, based on anisotropic waveguides, an optical switch with an on/off ratio of 2.14 is built up in a 2D CdS branched nanowire array. Because the branches are obliquely distributed at the same side of the trunk in a highly ordered form, the guided photoluminescence (PL) intensity from the trunk into the branch tightly relates to its angle. Based on the different intensity of the guided PL emitted from the end of each branch, the position of the incident spot in the backbone area can be identified accurately, making a feasible construction of an on-chip position-sensitive detector to realize an all-optical information process.