Reflective Amplified Recirculating Delay Line Bandpass Filter

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A new microwave photonic filter structure that can achieve a high <formula formulatype="inline"><tex>Q</tex> </formula> factor, high stopband rejection, and high skirt selectivity bandpass filter response simultaneously is presented. It is based on reflecting the signal back into a single amplified optical recirculating delay line and comprises coherent summation of the multiple signals that constitute each tap and incoherent summation of the successive taps. This introduces a new class of filter operation and effectively enables the realization of a higher order bandpass filter characteristic in a very simple structure. Experimental results are presented that demonstrate a multiple-tap high-<formula formulatype="inline"><tex>Q</tex></formula> bandpass filter response that also displays high stopband rejection level and high skirt selectivity. </para>