Flexible tunable spectrum sliced microwave photonic filter using parallel Fabry-Pérot filters and Fiber Bragg Grating

A simple and low-cost spectrum sliced microwave photonic filter with high tunability has been implemented. This is based on use of two Fabry-Pérot filters with same free spectral range connected in parallel but one filter with an external fiber delay. An extension of this configuration with Fiber Bragg Grating (FBG) as delay element is also demonstrated. This architecture overcomes the tuning difficulties of a single Fabry-Pérot filter employed as a slicing element. Flexible tunability, large overall free spectral range and high quality factor have been obtained with the proposed configuration owing to the use of fiber delay/FBG. Wide and step tuning has been achieved in the frequency range of 41.1GHz to 50.23GHz in steps of 2.28GHz. The additional components are another Fabry-Pérot filter and fiber delay/FBG which makes the proposed architecture highly compact and cost-effective. Most of the practical difficulties faced in use of optical fiber are eliminated using FBGs. The characteristics of proposed configuration with different applied delays using fiber and FBG were tabulated. An analysis of flexible tunable property of the filter was made in terms of length of fiber delay and grating length of FBG and the results were plotted. Also quality factor calculation of the proposed filter was discussed.