Long-Period Grating Relative Humidity Sensor With Hydrogel Coating

Abstract

High-sensitivity sensor of low relative humidity based on overlay on side-polished fibersABSTRACT: In this article, a miniaturized rectangular printed antenna that meets the ultrawideband (UWB) characteristics in terms of bandwidth and reflection coefficient is proposed. The designed antenna with dimension of 25316 mm 2 (L 3 W) was fabricated on FR-4 epoxy dielectric with relative permittivity of 4.4. SMA female connector is used for feeding with characteristic impedance of 50 X. The antenna exhibits good UWB characteristics and has the capability of operating between 3.92 to 11.32 GHz. The proposed antenna has omnidirectional radiation pattern on most of the operating band. The measured reflection coefficient of the proposed antenna is compared with the simulated one; good agreement is observed. Also, radiation pattern and gain of the antenna are presented. All simulations are carried out using the EM commercial simulators, HFSS, and CST.

photonic sensors review progress of optical fiber sensors and its application in harsh environment

“…The transmission spectrum of cascaded LFPGs shown in Fig. 3 contains several sinusoidal interference fringes exhibiting an envelope corresponding to the attenuation bands normally presented for single LFPG [2][3]. When being coated with hydrogel or palladium silver (Pd-Ag) film, the cascaded LFPGs can be used as relative humidity (RH) sensors or hydrogen (H 2 ) sensors respectively, which is useful for strategic weapon storage where the space is airtight and cramped, and conventional electrical humidity sensors cannot be used.…”

Humidity sensor based on a single-mode hetero-core fiber structure

“…Compared with electronic RH sensors, optical fiber based RH sensors offer numerous advantages, such as immunity to electromagnetic interference, small size, low weight, and remote monitoring. A wide range of RH sensing techniques based on optical fibers has been reported previously, including long period gratings (LPG) [1][2][3], fiber Bragg gratings [4,5], side polished fibers [6], plastic optical fibers [7], surface plasmon resonance [8,9], photonic crystal fiber interferometer [10], and tapered optical fibers [11,12]. Recently Akita proposed to use a heterocore optical fiber as a humidity sensor, which is based on a multimode-singlemode-multimode fiber structure with the benefits of simplicity and low cost [13].…”

“…However, if a different humidity-sensitive material is used as a coating, for example, hydrogel [1], which is stable in a high humidity range up to 100%, then this SMF28-SCSMF-SMF28 fiber structure based RH sensor can be used to measure RH values up to 100% RH.…”

Long Period Fibre Gratings

“…Fibre gratings are very sensitive to physical perturbations like temperature, strain, and pressure (Othonos & Kalli, 1999;Kersey et. al., 1997), however, in combination with a suitable transducer can monitor other magnitudes such as humidity (Liu et. al., 2007), or electric fields (Abramov et.…”