As interleavers have a fairly high cost-performance
they have been extensively used in narrow interval DWDM sys-tems.This paper introduces a kind of technology
by which a new type of polarization delay structure is used to manufacture narrow-channel-interval interleavers
which are characteristic of small in insertion loss
polarization dependent loss and polari-zation mode dispersion
and easy in assembly.In addition
the paper describes in detail the basic theory and design concept of the polarization delay structure and the structure of the interleaver manufactured thereby.