Roberson A. Oliveira

Acousto-Optic Effect in Microstructured Polymer Fiber Bragg Gratings: Simulation and Experimental Overview

A fine control of the microstructured polymer fiber Bragg grating spectrum properties, such as maximum reflected power and 3-dB bandwidth, through acousto-optic modulation is presented. For simulation purposes, the device is modelled as a single structure, comprising a silica horn and a fiber Bragg grating. For similar sized structures a good correlation between the numerical results and the experimental data is obtained, allowing the strain field to be completely characterized along the whole structure. It is also shown that the microstructured polymer fiber Bragg grating requires less effort from the piezoelectric actuator to produce modification in the grating spectrum when compared with a silica fiber Bragg grating. This technique has potential to be applied on tunable optical filters and tunable cavities for photonic applications.

Bragg grating writing in acoustically excited optical fiber

Direct grating writing was modified by adding an acousto optic modulator in the optical fibre assembly. The acoustic wave changes the properties of the fibre while the beam is scanned along the fiber, creating a complex FBG profile that depends on the acoustic driver parameters.

Control of the long period grating spectrum through low frequency flexural acoustic waves

We have shown experimental results of the excitation of long period fiber gratings by means of flexural acoustic waves with a wavelength larger than the grating period, validated by numerical simulations. The effect of the acoustic wave on the grating is modeled with the method of assumed modes, which delivers the strain field inside the grating, then used as the input to the transfer matrix method, needed for calculating the grating spectrum. The experimental and numerical results are found to be in good agreement, even though only the strain-optic effects are taken into account.

Complex Bragg grating writing using direct modulation of the optical fiber with flexural waves

A flexural wave is applied to an optical fiber during the process of Bragg grating inscription using the direct writing method through a phase mask. Using this approach, we can dither the writing process to allow complex grating writing. Examples we demonstrate are tunable sampled gratings and phase-shifted gratings.

Control of the properties of fiber Bragg gratings based on the acousto-optic effect

A method for a fast and fine control of a notch filter and the group delay of a fiber Bragg grating (FBG) is presented. The method is based on the acousto-optic effect in fibers.

Production and characterization of Bragg gratings in polymer optical fibers for sensors and optical communications

The inscription of Bragg gratings in different POFs, including GI-POF is presented. Additionally the cross-sensitivity characterization to temperature and strain for an mPOF FBG is reported for the first time. Results show better sensitivity performances after the annealing process which will help to develop new sensitive optical devices.

Tunable acoustic bursts for customized tapered fiber Bragg structures

The inscription of customized fiber Bragg structures under acoustic excitation is proposed and demonstrated. By setting the proper acoustic excitation function, the desired spectrum of the grating can be achieved. In this paper, the effect of applying a burst acoustic wave during the process of Bragg grating inscription using the direct writing method through a phase mask is investigated. Among all the characteristics that can be changed due to a periodic defect insertion in the uniform Bragg structure, the control of phase is used to demonstrate this assertion. The results of numerical simulations are shown to be in excellent agreement with experiments. It can be further extended to generate multiple phase shifts in optical fiber and/or waveguides, if the defects are inserted at different positions, as is shown.

Single device for excitation of both flexural and longitudinal acousto-optic effects in fiber Bragg gratings

Experimental results on the acoustic modulation of fiber Bragg gratings are presented. Two main effects are achieved for the acousto-optic effect, one due to the longitudinal vibration mode of the fiber and the other due to the flexural mode. Using the flexural effect, the FBG reflectivity can be attenuated up to 26 dB, with a switching time of 63 ¿s. Using the longitudinal effect, lateral lobules separated by 0.3 nm can be induced.

Fast acousto-optic add-drop based on fiber bragg grating

A fast add-drop multiplexer based on the acousto-optic effect is demonstrated. The measured switching time is 61 mus, obtained with a fiber-horn structure arranged along the fiber axis.

Analysis of Mechanical Properties of a Photonic Crystal Fiber Bragg Grating Acousto‐Optic Modulator

In this work the mechanical properties of a Photonic Crystal Fiber is achieved using concepts of the rules of mixture of composite materials in order to find the effective area, effective Young’s modulus and the effective density. Results achieved by analytical method are compared to results achieved through a commercial software. Simulation results of acoustic‐induced modulation of a Photonic Crystal Fiber Bragg grating obtained using adapted Finite Element and Transfer Matrix Methods is showed. The methodology applied to study the device consists of the achieving of Photonic Crystal Fiber mechanical properties; the strain field in the whole structure is obtained by using the Finite Element Method. Further, the calculated strain field is used on the Transfer Matrix algorithm to obtain the Fiber Bragg Gratings reflected spectrum. The results are compared with conventional Fiber Bragg Gratings Acousto‐Optic modulator. Numerical results show that, due to its smaller stiffness, compared to conventional Fiber...