All-fiber tunable microwave photonic filter based on a cladding-mode coupler

We demonstrate an all-fiber tunable microwave photonic filter based on the configuration of a MachZehnder interferometer, which employs two fixed widely separated wavelengths and a cladding-mode coupler formed with a pair of matching long-period fiber gratings to provide continuous tuning of the time-delay difference between the two arms of the interferometer. The filter provides stable coherence-free operation and a free spectral range that can be tuned continuously and precisely over a wide range. © 2006 IEEE.