Double coupler amplified recirculating delay line microwave photonic bandpass filter

Theoretical and experimental investigations on a double coupler amplified recirculating delay line (ARDL) microwave photonic bandpass filter are presented. These show that the system involves both coherent and incoherent summation of optical signals. This enables a higher order filter transfer function to be realized, which results in a high-performance frequency response that cannot be achieved by the conventional single coupler ARDL structure. Experimental results are presented that demonstrate a sharp, high skirt selectivity and high stopband rejection level bandpass filter response.