Abstract: The model of the defect of 1-D photonic crystal, which is detect in symmetry, is set up oaseu on the solution of eigen matrix. Three instances are simulated by computer. Comparing the transmission spectrum of simulation with one of F-P cavity, it is concluded that the optical path of the defect is equivalent to one of F -P cavity only in specific condition, they are not equivalent in common conditon.

Key words: photonic crystal, defect, eigen matrix, simulation, F-P cavity