摘要

In conventional approaches to realizing microwave photonic filters (MPFs) with rectangular response, both positive and negative coefficients should be included in the systems, which is a difficulty in incoherent MPFs. Electrical or optical ways to realize the MPFs with bipolar taps, such as those using balanced detectors or based on two opposite modulation slopes of dual-input Mach-Zehnder modulators, usually involve more components compared with the MPFs with unipolar taps. In this Letter, a design of MPFs with rectangular response using all positive coefficients is proposed. There is only one optical link as well as one photodetector utilized in the approach, which largely simplifies the filter structure. Experimental demonstrations of 55-positive-tap MPFs with different passbands are presented to verify the feasibility and potential of the approach.