FBG in polymer optical fibers (POFs) is a promising technology for a wide range of sensing applications due to a lower Young’s modulus and a large range of applying strain. Furthermore, POFs have several properties which make them attractive for biosensing applications such as nonbrittle nature, flexibility in bending and biocompatibility. Chirped Fiber Bragg gratings (CFBGs), which are characterized by a nonuniform modulation of the refractive index show a broad reflection spectrum, enabling shortlength distributed sensing. The combining benefits of POF and CFBGs is attractive for biomedical applications. Here, we present a novel method to obtain CFBG in POF with a postprocess uniform POF FBG by using resin.
In this work, we report on a simple, but highly sensitive sensor based on two intrinsic Fabry-Pérot interferometers (FPI) inscribed in a standard optical fiber. A brief theoretical study on the Vernier effect is presented, followed by a simulation of the FPIs physical characteristics to achieve the desired sensitivity enhanced factor. Based on the simulation results, the FPIs were fabricated using a custom micromachining setup based on a near-infrared femtosecond laser and a motorized XYZ platform. A real-time monitoring was performed throughout the entire process, by visualizing the inscription with a CCD camera and recording the resulted spectra. High-resolution was demonstrated for the manufactured devices, achieving, in the best-case, values of ~7 nε and 0.001°C for strain and temperature, respectively. The sensor’s performance allied with its versatile and customizable configuration allows an operando and in-situ strain and temperature monitoring under harsh environments.
In this paper, the design and implementation of a cost-effective interrogation architecture, for dynamic strain monitoring of in-line Fabry-Perot interferometric (FPI) optical fiber sensors is presented. The common interrogation techniques for this type of sensors are based in the full spectrum analysis, which render them not adequate for dynamic/high frequency monitoring applications. In this work, we propose an alternative cost-effective solution, based on a simplified edge-filter technique, for the dynamic monitoring of FPI sensing devices. The FPI based sensor was produced from the recycling of optical fiber previously damaged by the catastrophic fuse effect using precise splicing techniques. A characterization was performed with two different devices, an optical spectrum analyzer (OSA) and the proposed device leading to similar behavior and sensitivity values.
We report on a thermal stability study of the resonant wavelength of fiber Bragg gratings fabricated by femtosecond laser. We propose a new method to analyze the decay of the central wavelength shift of Bragg gratings based on isothermal and isochronal processes up-to a maximum temperature of 800°C. The obtained thermal decay follows a typical power-law function, which allowed us to fit theoretical equations to our experimental data and simulate the refractive index decay. A method to mitigate this decay is proposed and the results demonstrate the potential of using femtosecond fiber Bragg gratings as high temperature sensors.
In this work, an optical fiber hydrostatic pressure sensor based in Fabry-Perot micro-cavities is presented. These micro structures were generated by the recycling of optical fiber previously damaged by the fiber fuse effect, resulting in a cost effective solution when compared with the traditional methods used to produce similar micro-cavities. The developed sensor was tested for pressures ranging from 20.0 to 190.0 cmH2O and a sensitivity of 53.7 ± 2.6 pm/cmH2O for hydrostatic pressures below to 100 cmH2O was achieved.