Maria J. Erro

Multiple-frequency-tuned photonic bandgap microstrip structures

Photonic bandgap (PBG) structures in microstrip technology have been recently proposed as efficient Bragg reflectors. The periodic patterns employed until now were formed by a distribution of nonconnected holes (cermet topology) etched in the ground plane or drilled in the dielectric substrate, giving rise to single-frequency-tuned band reflectors. In this letter, a novel pattern that follows a continuous profile (network topology) is proposed to simultaneously reject multiple frequency bands. It is formed by the addition of various sinusoidal functions tuned at the design frequencies. Measurements performed for two-and three-frequency-tuned PBG microstrip prototypes show that multiple deep and wide stopbands can be obtained using these novel devices.

Real-time spectrum analysis in microstrip technology

We report on a time-domain analog in microwave lines to the spatial Fraunhofer (far-field) diffraction in paraxial conditions. Microstrip lines are used to design filtering configurations acting as spectrum analyzers. They are based on linearly chirped distributed Bragg coupling between the fundamental microstrip mode and the same but counterpropagating mode. Linearly chirped continuous impedance modulation in a microstrip line with varying upper plane strip-width is shown to yield a mode-coupling location and group delay linearly distributed in frequency. Under the condition of a temporal equivalent to the spatial Fraunhofer inequality, the energy spectral density of the input signal is directly recoverable from the average output (reflected) power. It is only necessary to take into account a linear axis-change, given by the dispersion coefficient (group-delay slope) of the structure, from time to Fourier frequency. Both pulsed and nonpulsed RF signals are studied. Sequential time-gated segments of the input have to be processed in the nonpulsed case. The maximum frequency resolution achievable in this situation is discussed. The devices developed here could have important potential applications in the field of temporal signal processing, such as filtering using time-division techniques.

Periodic Time-Domain Modulation for the Electrically Tunable Control of Optical Pulse Train Envelope and Repetition Rate Multiplication

An electrically tunable system for the control of optical pulse sequences is proposed and demonstrated. It is based on the use of an electrooptic modulator for periodic phase modulation followed by a dispersive device to obtain the temporal Talbot effect. The proposed configuration allows for repetition rate multiplication with different multiplication factors and with the simultaneous control of the pulse train envelope by simply changing the electrical signal driving the modulator. Simulated and experimental results for an input optical pulse train of 10 GHz are shown for different multiplication factors and envelope shapes.

Emulated single-mode fiber-optic link by use of a linearly chirped fiber Bragg grating

A compact and low-cost device that emulates a standard and dispersion-shifted 100-km single-mode fiber-optic link at 1550 nm is proposed. The device, composed of a chirped fiber grating and a monitor coupler, is analyzed by simulation and experimentally proved. A chirped fiber grating synthesis procedure and an explanation for both cases are also introduced.

On the Measurement of Fiber Bragg Grating's Phase Responses and the Applicability of Phase Reconstruction Methods

A signal processing algorithm is used to reconstruct the phase response of fiber Bragg gratings from easy-to-obtain module data. The algorithm is applied to optical spectrum analyzer measurements, avoiding the use of costly and complex equipment for the direct measurement of the complete frequency response. Reconstructed results, both in transmission and reflection, are then validated by comparison with three of the most common experimental techniques (interferometric, modulation phase shift, and single-sideband modulation).

Spectrally Efficient Phase Encoded Optical CDMA System in Time Domain

A novel WDM-compatible spectrally phase encoded-optical CDMA scheme based on second order dispersion is presented. Proof of concept results are given for a system transmitting at 2.5 Gbps within an 80 GHz optical window.

Applications of Electromagnetic Crystals in Microstrip Technology

Recently, new promising periodic structures called Photonic Crystals, or more generally Electromagnetic Crystal structures, have been considered for both microwave and photonic applications. Planar microstrip waveguides are very attractive in microwave engineering where several innovative designs have been proposed to expand the scope of application of the new Photonic Crystal concepts to the well established microwave domain. Recent configurations are presented for these new promising applications both in microwave and millimetre wave integrated circuits and antennas.

Optical carrier proccessor of microwave/millimeter-wave photonic signals by using a fiber Bragg grating in transmission

We propose and demonstrate the use of a fiber Bragg grating operated in transmission to build a simple, low-cost and efficient optical carrier processor that permits to enhance the fiber-optic transmission of RF signals. It simultaneously achieves an improvement in the detected electric power level by partially attenuating the optical carrier and the capability of reconfiguring the link frequency response avoiding the carrier suppression effect due to the fiber-optic chromatic dispersion.

CHIRPED FIBER GRATING-BASED FIBER OPTIC COMMUNICATION EVALUATOR : DESIGN AND IMPLEMENTATION

A compact and low-cost device that emulates a 100-km single-mode fiber optic link at 1550 nm is proposed. The device, composed of a chirped fiber grating and a monitor coupler, is analyzed by simulation and experimentally proved. A chirped fiber grating synthesis procedure is also introduced.