All-optical transversal filter with tap doubling and negative coefficients based on polarization modulation

Area of Science:

• Photonics and optical engineering
• Materials science utilizing electro-optic effects
• Signal processing with optical components

Background:

• Traditional transversal filters often require complex electronic components.
• Achieving negative coefficients in optical filters presents significant challenges.
• Integrating multiple functionalities like tap doubling and negative coefficients is difficult.

Purpose of the Study:

• To propose and demonstrate a novel all-optical transversal filter.
• To achieve simultaneous generation of negative and positive filter coefficients.
• To enable tap doubling and coherent interference-free operation using optical means.

Main Methods:

• Utilizing polarization modulation based on the electro-optic effect in Lithium Niobate (LiNbO(3)) crystals.
• Employing wavelength- and polarization-dependent time delays in optical fiber for tap doubling.
• Synthesizing filter taps directly in the optical domain.

Main Results:

• Simultaneous generation of negative and positive coefficients was achieved.
• Tap doubling was successfully implemented using fiber optic delays.
• Stable 6-tap bandpass filter characteristics were experimentally demonstrated.
• The filter operated without coherent interference due to orthogonal polarity.

Conclusions:

• The proposed all-optical transversal filter offers a new approach for optical signal processing.
• The use of LiNbO(3) and fiber optics provides a robust method for generating complex filter responses.
• This technology enables efficient and stable optical filtering with reduced complexity.