Optical Transversal Filter With Variable Weights

Abstract

We describe an optical transversal filter constructed from off-the-shelf components. The filter is comprised of fiber optics and integrated optical devices. This filter differs significantly from previously constructed filters which all had fixed tap weights,1-3 usually of value unity. An approach used to make fixed weight taps was to produce dielectric mirrors directly in the fiber.3 All of these systems were limited by the inflexibility of their weighting scheme. This limitation adversely affects the filter performance in two ways. First, it is not possible to change the response function of the filter once the filter has been made. Second, it is not possible to correct for tap weight errors. When a fiber optic transversal filter is built, by any technique, there will be some error in the value of the loss and the delay between taps. Fixed weight systems have no technique for self correction.