Tunable microwave photonic transversal filter

Abstract

We present a tapped tunable delay line filter for radiofrequency (RF) photonic filtering applications, capable of rapid tunability over a wide RF bandwidth limited only by the optical components’ losses, while maintaining independence from polarization state. Multiple fiber taps with contrasting dispersion slopes are used in intensity-modulated direct detection microwave photonic links. A temporal delay is generated between the signals within each arm of the link. Once a signal is received using balanced differential detection, nulls are generated as a function of the laser's operating wavelength. Tuning of the laser allows for a rapid shifting of the nulls in the RF spectrum to dynamically mitigate co-site interference. Through this method we demonstrate the potential for rapid tunability over the RF spectrum by the variation of the operating wavelength of the optical carrier.