Multistage All-pass Filter Compensating The Dispersion Introduced By The Thin Film Filter

With the increasing individual bit rate, the dispersion compensation become more andmore important. The dispersion associated with thin-film filters, which has not been studied indetail before, should be considered. Since the dispersion introduced by thin-film filters isdifferent from the dispersion of fiber, the compensation for the dispersions of fiber andthin-film filter are different. Then it is necessary to introduce a novel dispersion compensationbased on all-pass optical filters. At first this paper presents the principle of the all-pass optical filter and gives thedispersion formula of single-stage optical filter, then analyzes the effect of the structuralparameter on the dispersion. Then it is concluded that the single-stage optical filter can notmeet the demand. So the multistage optical all-pass filter is brought forward, the dispersionof which can compensate the dispersion introduced by thin-film filter. And the theoreticaldispersion graph of four-stage optical all-pass filter is presented. After the dispersion graph, architectures of circulator and two-fiber collimator are shown.It is the two-fiber collimator that is used in the sample, so it's architecture is offered in detail,including the ray track, the theoretical loss and the relationship between the distance of twofibers and the station of the dispersion graph. At last this paper gives the tested loss graph and dispersion graph of the sample, whichare consistent approximately compared with the theoretical loss and dispersion. Thedifference between the theoretical data and the tested data are analyzed and explained.