All-optical WDM multi-tap microwave filter with flat bandpass.

Area of Science:

• Photonics
• Microwave Engineering
• Optical Signal Processing

Background:

• Photonic microwave filters offer high performance but often struggle with implementing complex coefficient values.
• Existing methods for generating negative coefficients in photonic filters are limited.

Purpose of the Study:

• To propose and demonstrate a novel incoherent photonic microwave filter capable of implementing multiple positive and negative coefficients.
• To validate the filter's design using the Parks-McClellan algorithm for practical applications.

Main Methods:

• Utilizing two sets of optical carriers and dispersive media for filter implementation.
• Achieving positive and negative coefficients through pi phase inversion in an electro-optic Mach-Zehnder modulator and its wavelength-dependent Vpi.
• Designing a 5-tap flat bandpass filter using the Parks-McClellan algorithm.

Main Results:

• Successful demonstration of an incoherent photonic microwave filter with both positive and negative coefficients.
• Experimental results for a 5-tap bandpass filter closely matched theoretical predictions.
• Validation of the modulator's Vpi dependence with wavelength for coefficient control.

Conclusions:

• The proposed technique effectively implements multiple positive and negative coefficients in photonic microwave filters.
• The demonstrated method is feasible for designing practical filter transfer functions.
• This approach advances the capabilities of photonic signal processing for microwave applications.