Beatriz Ortega

Discrete-time optical Processing of microwave signals

This paper presents the fundamental principles and recent advances in the field of photonic filtering of microwave signals using discrete-time incoherent processing. We also provide a comprehensive review of the fundamentals, applications, and current state of the art.

New and flexible fiber-optic delay-line filters using chirped Bragg gratings and laser arrays

We propose a novel kind of radio-frequency filters that are composed by a linearly chirped fiber grating and a laser array. These structures are capable of providing full transfer-function reconfiguration and resonance tunability. A thorough theoretical modeling and operation features are provided along with the experimental demonstration of the proposed features.

Photonic microwave tunable single-bandpass filter based on a Mach-Zehnder interferometer

The authors present the theoretical analysis and experimental demonstration of a novel single-bandpass tunable microwave filter. The filter is based on a broadband optical source and a fiber Mach-Zehnder interferometer and shows a high Q factor over a tuning range of 5-17 GHz. A generalized analysis considering that the optical signal propagates along optical delay lines with a dispersion slope different from zero is presented.

Microwave photonic filters with negative coefficients based on phase inversion in an electro-optic modulator

We report on a novel technical approach to the implementation of photonic rf filters that is based on the pi phase inversion that a rf modulating signal suffers in an electro-optic Mach-Zehnder modulator, which depends on whether the positive or the negative linear slope of the signals modulation transfer function is employed. Experimental evidence is provided of the implementation of filters with negative coefficients that shows excellent agreement with results predicted by the theory.

Optical UWB pulse generator using an N tap microwave photonic filter and phase inversion adaptable to different pulse modulation formats

We propose theoretically and demonstrate experimentally an optical architecture for flexible Ultra-Wideband pulse generation. It is based on an N-tap reconfigurable microwave photonic filter fed by a laser array by using phase inversion in a Mach-Zehnder modulator. Since a large number of positive and negative coefficients can be easily implemented, UWB pulses fitted to the FCC mask requirements can be generated. As an example, a four tap pulse generator is experimentally demonstrated which complies with the FCC regulation. The proposed pulse generator allows different pulse modulation formats since the amplitude, polarity and time delay of generated pulse is controlled.

Variable delay line for phased-array antenna based on a chirped fiber grating

We present a theoretical and experimental analysis of the performance of phased-array antennas steered by a single chirped fiber grating. Two approaches consisting of conventional and single-sideband (SSB) modulation techniques of the optical signal are presented in order to compare their performance and suitability for beamforming applications in microwave antennas. By using a 40-cm-long chirped grating, we measure the phase and amplitude response and calculate the corresponding radiation patterns to demonstrate wide-band operation and continuous spatial scanning properties of both configurations. SSB modulation Is presented as a real alternative to the first one offering broader operation band (4-18 GHz) for a given chirped grating and being less demanding on the fiber grating characteristics.

Tunable all-optical negative multitap microwave filters based on uniform fiber Bragg gratings.

We present a novel and simple technique for obtaining transversal filters with negative coefficients by using uniform fiber Bragg gratings. We demonstrate a wide tuning range, good performance, low cost, and easy implementation of multitap filters in an all-optical passive configuration in which negative taps are obtained by use of the transmission of a broadband source through uniform Bragg gratings.

Optical microwave filter based on spectral slicing by use of arrayed waveguide gratings

We have experimentally demonstrated a new optical signal processor based on the use of arrayed waveguide gratings. The structure exploits the concept of spectral slicing combined with the use of an optical dispersive medium. The approach presents increased flexibility from previous slicing-based structures in terms of tunability, reconfiguration, and apodization of the samples or coefficients of the transversal optical filter.

Microwave photonic filters using low-cost sources featuring tunability, reconfigurability and negative coefficients

We propose and experimentally demonstrate two configurations of photonic filters for the processing of microwave signals featuring tunability, reconfigurability and negative coefficients based on the use of low cost optical sources. The first option is a low power configuration based on spectral slicing of a broadband source. The second is a high power configuration based on fixed lasers. Tunability, reconfigurability and negative coefficients are achieved by means of a MEMS cross-connect, a variable optical attenuator array and simple 2x2 switches respectively.

Broad-band tunable microwave transversal notch filter based on tunable uniform fiber Bragg gratings as slicing filters

We demonstrate a multigigahertz tunable transversal notch filter based on two uniform fiber Bragg gratings as slicing elements of a broad-band optical source. The tunability of the filter is achieved by wavelength tuning of the fiber gratings to adjust the basic time delay provided by a dispersive element.