Photonic switching, is an essential synergetic approach in optical networks, providing virtually unlimited communication bandwidth and transparency to the data rate and encoding, has been developed to provide high bandwidth and avoid the repeated optical-to-electrical (O/E) and electrical-to-optical (E/O) signal conversions. The 2 X 2 directional coupler is a common switching element used in photonic switching networks. Due to the imperfect coupling energy in one path through the another path, crosstalk occurs. A faulty switch is defined as a switch that produces crosstalk beyond the acceptable level. A blocking network, say Dilated Omega Networks (DON), are discussed. One of the characteristics of DON is that the input signal and crosstalk signal will not pass through the same output switch. It relaxes the designs of diagnosing fault algorithm compared to that of Dilated Benes Networks, especially for the reduction of test needed, saving time and effort for the cases, such as single-path-multiple-faults, multiple-path- multiple-faults and crosstalk symmetry. Detail proofs and more examples will be addressed in this paper.