The paper introduce a new interleaver/de interleaver technique used in WDM network. The principle and simple structure of a de interleaver based on polarization interference theory are discussed. According to the theory analysis and experiment conducted by the author, a means is brought forward to widen the bandwidth of output. Some other interleaver techniques are also referred in terms of their advantages and disadvantages. At last the author prospect the potential application and market of interleaver techniques.