High sensitivity LPG Mach–Zehnder sensor for real-time fuel conformity analysis

Abstract

A high sensitivity refractive index sensor based on the combination of mechanically induced long period gratings (LPG) and fiber tapers was developed for real-time fuel quality analysis. The sensor was built in a Mach-Zehnder configuration by employing a pair of in-series gratings. In order to enhance sensor sensitivity, the region between both LPGs was tapered down from 125 to 10 μm. The system was tested by measuring water concentration in ethanol and ethanol concentration in commercial gasoline. The tapered sensor has shown an average sensitivity of 930 nm/RIU, 18 times higher than the non-tapered version. The resolution limit of the system using spectral interrogation was estimated to be 0.06% of ethanol dissolved in gasoline. For the purpose of real-time monitoring, an interrogation system based on white light interferometry (WLI) and virtual instrumentation was employed to evaluate ethanol evaporation in water, avoiding the use of spectral analysis. The WLI system, using phase tracking techniques, enabled us to record the evolution of the ethanol concentration in water with a resolution of 0.005% (v/v).

Analysis of immersed silica optical microfiber knot resonator and its application as a moisture sensor

“…Another kind of interferometer widely used for sensing purposes is the multimodal one, in which interference occurs between traveling modes [3]. The development of techniques to produce low-loss microfibers from standard fibers allowed these sensors to have their sensitivity enhanced as a consequence of the stunning properties inherent to those micrometric fibers [4,5], such as high associated evanescent field and dispersion engineering. Directly connected to this class of microwaveguides, microfiber optical resonators could be introduced.…”

Gasoline Quality Sensor Based on Tilted Fiber Bragg Gratings

“…This result is similar to the one that can be calculated from the long-period grating-based sensor reported in [6], of around 1%. Other sensors, however, can achieve better resolution levels, such as the high-sensitivity gasoline sensor reported in [10], of 0.06%. However, the sensor reported herein has the advantage of being much more compact and robust than the one reported in [10], which is based on a pair of long-period gratings associated to a fiber taper (which decreases the sensor robustness).…”

“…Long-period gratings (LPG) [5,6], singlemode-multimode-singlemode (SMS) structures [7], and thinned Bragg gratings [8] are technologies able to evaluate fuel conformity. Moreover, gasoline sensors based on Fabry-Perot interferometers prepared on fiber tips [9] and on long-period gratings associated with fiber tapers [10] have been reported in the literature. However, in these investigations, the sensing experiments are based on spectral measurements [5][6][7][8][9] or make use of sophisticated interrogation schemes (such as the setup reported in [10], based on white light interferometry).…”

“…Moreover, gasoline sensors based on Fabry-Perot interferometers prepared on fiber tips [9] and on long-period gratings associated with fiber tapers [10] have been reported in the literature. However, in these investigations, the sensing experiments are based on spectral measurements [5][6][7][8][9] or make use of sophisticated interrogation schemes (such as the setup reported in [10], based on white light interferometry). Regarding the use of spectral measurements, even though they are highly useful for sensing, their realization involves the utilization of expensive optical spectrum analyzers, which can ultimately limit their application for practical purposes.…”

Refractive Index Measurement of Liquids Based on Microstructured Optical Fibers

“…The great importance of measuring the refractive index (RI) in order to characterize the optical properties of fluids has led, over the past decades, to the development of RI sensors for applications in several areas such as the measurement of salinity of water [1], fuel quality analysis [2], or biotechnology processes [3]. In addition, direct measurements of RI were shown to provide valuable information on drug/DNA interaction and cell growth [4,5].…”