Simultaneous Measurement of Refractive Index and Temperature Using a Hybrid Fiber Bragg Grating/Long-Period Fiber Grating Configuration

Abstract

A fiber optic sensing system for simultaneous measurement of refractive index and temperature, based on a hybrid fiber Bragg grating/long-period grating arrangement is described. The experimental results show that this setup has a good performance in terms of linearity and sensitivity, the ratiometric output changes 4%/0.001 RIU and 3.6%/ ı C, respectively. The sensor resolution for the refractive index is 2 10 5 RIU. The simultaneous measurement of the refractive index and temperature was demonstrated. The sensing configuration has the ability to be read-out in reflection and works in the telecommunications window.

Simultaneous Measurement of Humidity and Temperature Based on an SiO$_{2}$-Nanospheres Film Deposited on a Long-Period Grating In-Line With a Fiber Bragg Grating

“…The LPG resonance is also temperature-dependent, and discrimination is effectively achieved through the extra information provided by the resonant peak of the FBG. A similar temperature-compensation configuration was already demonstrated by Patrick et al [13] for simultaneous measurement of temperature and strain and by Jesus et al [14] in a refractive index and temperature simultaneous measurement. The proposed sensing structure also incorporates self-referencing characteristics, providing compensation to undesirable optical losses along the system that often plague intensity-based designs.…”

Fast-Response High-Temperature Microfiber Coupler Tip Thermometer

“…MFCT offers several advantages, including compactness, extremely high temperature measurement capabilities, fast response, easy connection with other fiberized optical components, simple fabrication and low cost. By setting a reference wavelength and measuring the intensity ratio between the two wavelengths, the sensitivity can be further improved and the error associated to the source power drift/oscillations can be minimized [15].…”

Flow cell with hybrid LPG and FBG optical fibre sensor for refractometric measurements

“…On the other hand a fiber Bragg grating (FBG) [7] is insensitive to external refractive index and fiber bending, but it has a well-known response to both temperature and strain [8]. Differently from what already exists in literature [4]- [6], the challenge aspect is both the realization of a closed flow cell of relatively low volume where the optical fiber gratings can be fixed securely, and a methodology to control the LPG cross-sensitivities towards other physical parameters.…”

“…Thanks to their sensitivity to external refractive index and all the other advantages offered by the optical fiber sensors, long period gratings (LPGs) have been proposed for refractometric measurements [1]- [6]. However, because of the influence of temperature, strain and fiber bending in the LPG response, it is crucial to control, correct and stabilize these parameters in order to measure accurately the refractive index changes.…”