The use of polarization controllers in microwave photonic filters based on cascaded Hi-Bi fibers

Cascaded Hi-Bi fibers have been used to realize tunable microwave photonic filters in a simple way. We demonstrate in this paper that in such structures, the filter response is sensitive to the optical carrier wavelength. This means that a tunable laser as the optical source may be necessary to achieve the desired filter response. However, we show here that polarization controllers introduced in the filter structure can be used to stabilize the filter response against variation in the optical carrier wavelength. With this modification, even with a fixed-wavelength laser source one can achieve the desired filter response.