A Tunable Microwave Photonic Filter With a Complex Coefficient Based on Polarization Modulation

Abstract

A tunable microwave photonic filter with a complex coefficient based on polarization modulation and a single laser source is proposed and demonstrated. Two outof-phase microwave signals with orthogonal polarization states are generated using a polarization modulator and then combined into one special polarization state to introduce certain phase shifts after filtering out one sideband. The tunability of the filter with the complex coefficient is achieved by adjusting the phase shifts between two taps. In addition, the frequency response of the proposed filter from 10 to 11 GHz with FSR of 400 MHz is measured.

All-Optical Continuously Tunable Flat-Passband Microwave Photonic Notch Filter

“…This technique can only provide discrete notch frequency tuning. Another technique, which enables continuous notch frequency tuning, was demonstrated by controlling the phases of different-wavelength optical carriers and sidebands according to (8) via the FD-OP while keeping the SMF length fixed at 20 km. The measured continuously tunable notch filter response is shown in Fig.…”

“…To avoid attenuation on other frequency components around the desired null, MPNFs are required to have a flat passband and a narrow notch width frequency response. Many MPNFs implemented using various techniques have been reported [3][4][5][6][7][8][9][10][11][12][13]. Infinite impulse response (IIR) structure based MPNFs [3] can realize a high resolution filter response but have limited free spectral range (FSR) which reduces the filter operating frequency range.…”

“…Approaches based on finite impulse response (FIR) structures have a robust frequency response that is independent of changes in environmental condition and is also independent of the input RF signal power. However, most previously reported FIR structure based MPNFs have been limited to only 2 taps [7][8][9], or to just 4 taps [10][11][12], which produce a response that is much too gradual, causing significant frequency-dependent attenuation in the required passband that can corrupt the wanted information signal itself. A technique has been proposed to realize a multiple-tap MPNF [13].…”

Complex-Coefficient Microwave Photonic Filter Based on Orthogonally Polarized Optical Single-Sideband Modulation

“…Complex-coefficient filters are able to keep the FSR and shape unchanged while tuning the center frequency, so they have the most potential for applications among the MPFs with different coefficients. Many MPFs with complex coefficients have been reported [2][3][4][5][6] including those based on SSB modulation [2], stimulated Brillouin scattering (SBS) [3], fiber Bragg grating (FBG) [4], programmable photonic processor [5]. However, the problem of bias drift is existed in the scheme based on SSB modulator.…”

Microwave photonic notch filter based on polarisation multiplexing and cross gain modulation in a semiconductor optical amplifier

“…However, for many applications, bandpass filters are highly desired but can only be realised through negative or complex coefficients. A tunable notch filter with complex negative coefficients has been proposed in [3, 4]. The filter allows precise control over the notch or centre frequency of the passband while keeping the free spectral range (FSR) constant.…”