Ilda Abe

Superimposed Bragg gratings in high-birefringence fibre optics: three-parameter simultaneous measurements

We used a pair of Bragg gratings written in high birefringence fibre optics to measure, simultaneously, longitudinal and transverse strain and temperature. The Bragg gratings are superimposed in the same position of the fibre optic, so as to behave as a punctual sensor. The sensitivity of the spectral response of the device to longitudinal strain, transverse strain and temperature are all characterized, and the results of its application as a three-parameter sensor are also presented.

Bragg gratings in normal and reduced diameter high birefringence fibre optics

Fibre optic Bragg gratings (FBGs) written in normal and reduced diameter high birefringence (HiBi) fibres are studied. Chemical etching is used to reduce the diameter of fibres while the optical properties of the FBG spectrum are measured. The results obtained agree qualitatively with the stress enhanced chemical etching. The birefringence of the fibre is determined as a function of the diameter. Optical characterization of the FBG under transverse strain and temperature is also performed. The results obtained show the feasibility of the simultaneous measurement of those parameters with a HiBi FBG sensor.

Determination of setting expansion of dental materials using fibre optical sensing

The use of fibre Bragg grating sensors to study dental materials like resin-based composite and gypsum products is reported. Two commercially available composite resins and three types of gypsum products were tested in order to determine polymerization contraction and setting expansion. Temperature and strain evolution during the hardening phase of the material were also obtained. The presented technique can be a good tool for dentists in order to better manipulate a material and predict how it will behave in vivo.

Multiplexed fiber optic Bragg grating sensors for strain and temperature measurements in power systems

In Brazil several groups develop Optical Fiber Sensors based on Wavelength Division Multiplexed Optical Bragg Gratings. We present a review of recent results obtained at our groups in the development of Optical Fiber Sensors to measure deformation (strain) or temperature in high voltage power transmission lines.

Self-pumped wide range wavelength converter

A new broadband orthogonal pump (BOP) four wave mixing (FWM) wavelength conversion scheme was demonstrated. The implemented set up shown conversion efficiencies higher than -20 dB and with less than 3 dB variation, for different conversion wavelengths. It is also more stable and cost effective when comparing to other BOP FWM wavelength conversion techniques, due to the reduction of the number of devices needed. The tunability of the HiBi fibre ring cavity Bragg grating structure (FBGS) along with the bit-error rate measurements for this wavelength converter is under investigation and will be reported.

Development of Bragg grating sensors at CEFET-PR

Abstract A report of activities in the development of fibre optic Bragg grating (FOBG) sensors at “Centro Federal de Educacao Tecnologica do Parana (CEFET-PR)” is given. Numerical simulation, experimental development, calibration procedures and application results are used to study FOBG sensors in mechanical, electrical and biomedical engineering.

Force Monitoring in a Maxilla Model and Dentition Using Optical Fiber Bragg Gratings

The aim of this work is to show the possibility of using fiber optic sensors to instrument inside parts of an artificial maxilla and measure internal tension transmitted by the orthodontic and orthopedic appliances to the dentition and the adjacent bone. Bragg gratings written in a standard optical fiber were used to monitor the maxillary teeth and a multiplexed fiber was used to monitor the surface of the maxillary bone, transversally to the longest axis of the teeth. A Universal Test Machine was used to evaluate the sensitivity of the sensor to the vertical and lateral forces applied on the teeth. A wavelength shift of approximately 0.30 nm was detected when applying loads ranging from 0 to 20 N. By applying forces using the standard orthodontic appliances installed on the dentition it was possible to detect a range of forces between 0.025 N to 0.035 N during the activation of the arch wire and extra-oral forces. The use of the internal sensors in an artificial model made possible the monitoring of the resulting forces on the internal parts of the teeth and at the position where the strain takes place within the maxilla. The sensors detected that the orthodontic forces were not transmitted to the surface of the maxilla. This information is important to elucidate and to correlate undesirable effects as tooth root absorption and local pain during the orthodontic treatment.

Modeling and production of high-birefringence FOBG sensors

Fiber Optic Bragg Grating Sensors are modeled and studied in high birefringence fiber. Coupled mode theory and multilayer approach are used to predict the spectral characteristics of the structure. Results are compared with experimental characterization of devices produced by UV light using the external method.

Nonlinear Temperature Dependence of Etched Fiber Bragg Gratings

In this work, we experimentally study the thermal sensitivity of etched fiber Bragg gratings immersed in surrounding media with high refractive index (1.444). The fiber diameter was reduced at four different values 15, 10, 9, and 8 mum. A nonlinear behavior is observed, due two combined effects: the silica thermo-optic effect that causes a red shift and the surrounding thermo-optic effect that causes a blue shift.

Regeneration of Bragg gratings in polarization maintaining optical fibers

We report the formation of thermal regenerated Bragg gratings in different types of polarization maintaining fiber optics. Experimental results about the modification of the polarized reflection bands as a function of the temperature, before and after the grating regeneration, are presented.