Reconfigurable Few-Mode Fiber-Based Microwave Photonic Filter

We experimentally demonstrate, for the first-time to our knowledge, tunable true-time delay line operation over a few-mode fiber link, in which the time delay can be continuously and widely tuned, from 46.3 to 105.6 ps, by simply sweeping the operating optical wavelength over the 35-nm range of the C-band. This has become possible thanks to the particular modal dispersion properties of the developed double-clad step-index few-mode fiber, as it features relatively evenly-spaced incremental chromatic dispersion values among 5 spatial modes. To date, it is the first time a dispersion-diversity FMF with this property has been experimentally reported. We assess the performance of this true-time delay line when applied to microwave signal filtering in both space and wavelength diversities, where a variety of reconfigurable 5, 7 and 10-tap microwave filters with free spectral ranges ranging from 7.7 to 27.1 GHz are experimentally demonstrated.