Analysis of a microwave time delay line based on a perturbed uniform fiber Bragg grating operating at constant wavelength

This paper presents the modeling of a new microwave time delay line based on a uniform fiber Bragg grating (FBG) with a section which period has been perturbed. The time delay can be modified by changing the position of the perturbation along the grating. Theoretical results are presented for a 5-cm long uniform grating and optical signal is modulated up to 18 GHz. Experimental setup used magnetic fields to change the period locally along the grating and a 330 ps maximum time delay is shown. Comparison between calculations and measurements show a perfect agreement. Such a delay line offers many advantages for beamforming applications in phased array antennas where the operation at a fixed wavelength is required in order to simplify the architecture of these systems.