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

Abstract

A novel all-optical transversal filter with negative coefficients and tap doubling is proposed and experimentally demonstrated. Based on polarization modulation using the anisotropy of the electro-optic coefficient of LiNbO(3) crystals, negative and positive coefficients are simultaneously generated. Tap doubling is also achieved by using wavelength- and polarization-dependent time delays in fiber. Due to the orthogonal polarity between the two coefficients of each wavelength, the proposed filter is free from coherent interference and the synthesis of filter taps is performed in the optical domain. The experimental results demonstrated that stable 6-tap bandpass filter characteristics can be obtained by using only three optical sources.

All-Optical Tunable Multitap Microwave Photonic Filter Enabled by Fiber Optical Parametric Amplifier

“…However the structure was complex, requiring arrays of PDs and optical delay lines, while the electronic synthesizer for the taps imposed additional bandwidth limitation on the filter, and moreover it could not be tuned. MPF based on polarization modulation was reported in [10], which was also not tunable. Another method used broadband source slicing and a 2 × 1 integrated Mach-Zehnder modulator [11], however the increased noise level could jeopardize the performance and the specially designed modulator increases the cost.…”