Date Added: Jan 2012
All Pass Filters (APFs) are used in dispersion compensation which is the foremost requirement in an optical fiber link. All pass filters can correct any order of dispersion by the careful design of multistage all pass filters starting from very simple components with the use of N port devices. Multiple channels, as in Wavelength Division Multiplexed (WDM) system, can be compensated with a single device since these filters are periodic in phase response. The design technique and implementation of these filters has been discussed in this paper.