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

2000

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…

Fibre Bragg gratings tuned and chirped using magnetic fields

1997

The authors report on the use of magnetic fields in conjunction with magnetostrictive materials for tuning and chirping optical fibre Bragg gratings. The Bragg wavelength shifts as a consequence of the strain induced in the fibre by a magnetostrictive rod when a magnetic field is applied. A tuning range of 1.1 nm has been achieved by a magnetic field of 103 mT and the grating has been chirped by applying non-uniform magnetic fields.

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

2006

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.

Tuning And Chirping Fiber Bragg Gratings By A Magnetic Field

2005

Analysis of a microwave time delay line based on a perturbed uniform fiber Bragg grating operating at constant wavelength

2000

This paper presents the modeling of a new microwave time delay line based on a uniform fiber Bragg grating (FBG) with a section which period has been perturbed. The time delay can be modified by changing the position of the perturbation along the grating. Theoretical results are presented for a 5-cm long uniform grating and optical signal is modulated up to 18 GHz. Experimental setup used magnetic fields to change the period locally along the grating and a 330 ps maximum time delay is shown. Comparison between calculations and measurements show a perfect agreement. Such a delay line offers many advantages for beamforming applications in phased array antennas where the operation at a fixed w…

Uniform fibre Bragg gratings with an embedded perturbed section for multiple applications

1999

The interest in fibre Bragg gratings has been increased with the development of flexible fabrication techniques which are able to make gratings with any non-uniform characteristic (chirped, apodised, sampled, phase-shifted, etc.) required for an specific application [1].

Tunable and reconfigurable microwave filter by use of a Bragg-grating-based acousto-optic superlattice modulator

2005

We present an all-optical novel configuration for implementing multitap transversal filters by use of a broadband source sliced by fiber Bragg grating arrays generated by propagating an acoustic wave along a strong uniform fiber Bragg grating. The tunability and reconfigurability of the microwave filter are demonstrated.

Tunable dispersion device based on a tapered fiber Bragg grating and nonuniform magnetic fields

2003

We present a new variable dispersion device based on tuning the chirp of a tapered fiber Bragg grating by means of a magnetic transducer. By using a nonuniform magnetic field, we demonstrate a 188-472-ps/nm dispersion tuning range, suitable for tunable radio-frequency filters and dispersion compensation, among others.

Microwave phase shifter based on fibre Bragg grating

1998

A variable delay line is presented for phased array antennas based on a fibre Bragg grating which has a uniform period and operates at constant optical wavelength. The Bragg wavelength of a localised part of the fibre grating is modified by straining the fibre, the optical carrier is reflected by the strained part of the grating and the time delay of the microwave modulating signal is determined by the position where the strain has been applied. In this initial experiment time delay variations up to 330 ps in the frequency range 1 – 14 GHz have been achieved.

Accurate tuning of mismatched twin-core fiber filters

1998

We have demonstrated a reproducible and accurate way of tuning the coupling wavelength of a mismatched twin-core filter. This method allows high quality all-fiber filters to be implemented with low loss at any desired wavelength over a range of few hundred nanometers from the same fiber. An ~500-nm tuning range is demonstrated, limited only by the measurement setup and not by the technique itself. Highly accurate control of the filtering wavelength in combination with control of filtering strength by adjustment of the length of the twin-core fibers allows complex filter profiles to be implemented by cascading of several different filters. These filters are also very stable to a change in te…

Highly tunable optically switched time delay line for transversal filtering

2003

A novel tunable dispersion device, based on two chirped fibre gratings subjected to non-uniform magnetic fields, is presented. A large degree of tunability is achieved from 250 to 750 ps/nm. This is used to demonstrate RF filtering in the 3-11 GHz range.

White light sources filtered with fiber Bragg gratings for RF-photonics applications

2003

Abstract In this paper we demonstrate that broadband light emitters filtered with fiber Bragg gratings are a suitable light source for RF-photonics applications. A 0.075 nm bandwidth fiber grating illuminated by a light emitter of 40 nm bandwidth has been used as light source to feed a microwave phase shifter based on a chirped fiber Bragg grating. The device operates successfully in the tested frequency range (0.5–6) GHz and has been optically tuned in a range of 4 nm.

Photonic processing of microwave signals

2005

In this paper, recent advances in the implementation of photonic tuneable transversal filters for RF signal processing developed by the Optical Communications Group are described. After a brief introduction to the field and the basic concepts, limiting factors and application of these filters are described in the field. This is based on a distinction between filters based on wavelength tuneable optical taps and others based on the tuneability of the dispersive elements that provide the time delay between samples. Recently developed approaches have also been discussed.

Advanced Optical Processing of Microwave Signals

2005

The authors present a review on the recent approaches proposed to implement transversal RF filters. Different tunable transversal filters consisting of wavelength tunable optical taps and those employing the tunability of dispersive devices are presented showing their high-performance characteristics. A comprehensive review of the fundamentals and a discussion on the main limitation of these structures are also included.

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

2003

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.

Tunable chirped fibre Bragg grating device controlled by variable magnetic fields

2002

A novel dynamic chirping fibre Bragg grating device based on a magnetic field applied to a magnetostrictive transducer capable of tuning its dispersion is presented. Chirping ranges up to 300 ps/nm have been demonstrated, which are suitable for several applications such as tunable transversal filtering and dynamic dispersion compensation.

Chirped fibre Bragg gratings for phased-array antennas

1997

A variable delay line for phased-array antennas based on a chirped fibre Bragg grating is demonstrated. The time delay of a microwave modulating signal is modified by scanning in wavelength a chirped grating. In this initial experiment, time delay variations up to 556 ps have been achieved using a grating of 0.4 nm bandwidth and 6 cm length and modulating in the frequency range 390 MHz-5.20 GHz.

Automatic tunable and reconfigurable fiberoptic microwave filters based on a broadband optical source sliced by uniform fiber Bragg gratings.

2002

We demonstrate an automatic tunable transversal notch filter based on uniform fiber Bragg gratings and a broadband optical source. High tunability can be performed by stretching the fiber with the gratings written in series. Also, high sidelobe supression can be achieved by introducing tunable attenuators in a parallel configuration of the gratings.

Fully automatic simultaneous fiber grating amplitude and group delay characterization

1997

On the evaluation of an optical OFDM radio over FSO system with IM-DD for high-speed indoor communications

2017

En aquest article es proposa un nou sistema híbrid de ràdio sobre fibra (RoF) i òptica d’espai lliure (FSO) basat en la transmissió de senyals òptics OFDM (OOFDM) per proporcionar enllaços de comunicació sense fils òptics d’alta capacitat. Es proposa un esquema de transmissió de baix cost basat en IM-DD per simplificar i reutilitzar la infraestructura existent per desplegar un enllaç FSO d’alt ample de banda. Aquest article mostra els resultats experimentals basats en la implementació de l'esquema proposat sota una transmissió digital OOFDM de 16 QAM a través de 10 km de fibra monomode (SMF) i enllaç FSO de 300 mm. Els resultats mostren la viabilitat de desplegar un sistema de comunicació d…