Low-Pressure Measurement using an Extrinsic Fiber-Based Fabry-Perot Interferometer for Industrial Applications

The development of an extrinsic fiber-based Fabry-Perot interferometer (EFFPI) for low-pressure measurement in the industry applications has been studied in this work. Monochromatic light from a laser diode with a wavelength of 1310 nm is operated as a source for illuminating the EFFPI sensor. A 30 mm diameter PVC pipe is utilized as a target, of which one end is sealed with a rubber balloon and the end is connected to the air pressure flow controlling system. Furthermore, the center point of the balloon is secured with a reflective thin film, which has a reflectance of ~55%. For the performance validation of the fiber sensor, a low-pressure range from 5 to 50 mBar is released onto the target. With 12 rounds repeatability, the experimental results reported that the average measured pressure values from the EFFPI sensor are 4.915 – 50.988 mBar. When compared to the reference instrument, the maximum and average errors in percentage terms are, however, 3.77% and 1.45%, respectively. In addition, results showed that the measured pressure value is directly proportional to the number of interference fringes, giving a sensitivity in the pressure measurement of the EFFPI sensor of 0.248 mBar/fringe

Investigation of Fiber Optic-Based-Refractometer for Biogas Sensing

In this study, a fiber-based refractometer (FOR) applied for biogas sensing has been investigated. Two types of fiber, single-mode (SMF) and multimode fiber (MMF) have been proposed as sensing elements. The research aims to investigate the spot and power attenuation of both fiber types in 4 main conditions; fiber cladding, de-cladding, compound coating, and biogas feeding. The experimental results showed that the spot diameters from both fiber types are constantly at 4 and 26 mm in any conditions. This causes the difference in core diameters and also the dispersion of light characteristics within the fibers. Moreover, when the sensing element has been modified by the following conditions, the results indicated that the output intensity has proportionally changed, according to the fiber modification and the concentration of biogas absorbed into the sensing element. Besides, the power attenuation from MMF is larger than SMF. This causes the length of fiber de-cladding and dispersion of light within the MMF can easily be induced by biogas feeding. Therefore, it can be concluded that the MMF is more suitable than SMF for employment as a sensing element of the fiber refractometer