All-positive-coefficient microwave photonic filter with rectangular response.

Area of Science:

• Photonics
• Microwave Engineering
• Optical Signal Processing

Background:

• Conventional microwave photonic filters (MPFs) with rectangular responses require both positive and negative coefficients, posing challenges for incoherent systems.
• Existing methods for bipolar taps in MPFs often involve complex setups with multiple components, such as balanced detectors or dual-input Mach-Zehnder modulators.

Purpose of the Study:

• To propose a novel design for MPFs with a rectangular response that utilizes exclusively positive coefficients.
• To simplify the structure of MPFs by reducing the number of optical links and photodetectors.

Main Methods:

• A new design for MPFs is presented, employing only positive coefficients to achieve a rectangular frequency response.
• The proposed design integrates a single optical link and a single photodetector, significantly streamlining the filter architecture.

Main Results:

• Experimental validation of the proposed design was achieved through the demonstration of 55-tap MPFs.
• The fabricated filters exhibited rectangular responses with tunable passbands, confirming the feasibility of the approach.

Conclusions:

• The developed method offers a simplified and efficient approach to constructing MPFs with rectangular responses.
• The use of unipolar taps in this design presents a viable alternative to conventional bipolar tap implementations, paving the way for more compact and cost-effective photonic systems.