Optical Fiber Relative Humidity Sensor Research Articles

Highly Sensitive GO-ZnO Nanocomposite-Based Optical Fiber Relative Humidity Sensor

Highly Sensitive GO-ZnO Nanocomposite-Based Optical Fiber Relative Humidity Sensor

Miniature and high-performance optical fiber relative humidity sensor based on Fabry-Perot structure interacting with hydroxyethyl cellulose

A miniature Fabry-Perot fiber-optic sensor is demonstrated for high-performance relative humidity (RH) detection. This sensor is constructed by fusing a single-mode fiber to a small section of capillary coating the end with a hydroxyethyl cellulose film (HEC). The effects of capillary length and hydroxyethyl cellulose concentration on the RH response are investigated to obtain the preferential condition with capillary length of 102 μm and HEC concentration of 0.03 g/ml. A testing RH sensitivity of 1.24 nm/%RH can be achieved in the range of 48%RH to 60%RH. Simultaneously, small hysteresis errors are demonstrated in the tests with increasing and decreasing RH values. The dynamic measurements reveal a response time of 1.61 s and a recovery time of 2.1 s. The high sensitivity, good stability and simple fabrication process of the sensor make it promising for practical applications of relative humidity sensors.

Optical fiber humidity sensor with C60-THAM as molecule receptors

This study proposed a high sensitivity optical fiber relative humidity sensor (OFHS). Besides, a fullerene derivative, C 60 -THAM, was synthesized and firstly reported as a molecule receptor in the OFHS. Compared with the widely researched carbon-based materials in OFHS, the C 60 -THAM film has abundant amino dangling bonds, hence emerges naturally as excellent receptors for water molecules. Besides, a cascaded Fabry-Perot interferometer (FPI) was fabricated in the core of single-mode fiber (SMF) without surface damage by femtosecond laser. In the OFHS, the relative humidity (RH) was measured by the Vernier effect. The working principle of the OFHS was analyzed through calculation and simulation. In the experiment, C 60 -THAM was coated on the plant fiber end. The sensitivity of the sensor is about 0.42 nm/RH as the relative humidity change from 30% to 65% while the optical-matter reaction length is only about 150 nm. Moreover, the sensor exhibited a stable performance as the RH was decreasing from 65% to 30%. The OFHS in this work is fast response and the response time for the rising and decay process was about 2.2 s and 3.2 s respectively. • A fullerene derivative, C 60 -THAM, was synthesized and its application in the fiber humidity sensor was researched. • The humidity sensor is fast response and the rising and decay time is about 2.2 s and 3.2 s respecitively. • The sensitivity is 0.42 nm/RH as the humidity change from 30% to 65% while the optical-matter reaction length is 150 nm.

Performance evaluation of rose bengal dye-decorated plasmonic gold nanoparticles-coated fiber-optic humidity sensor: A mechanism for improved sensing

Low-cost fiber-optic humidity sensors with fast response became demanding. Thus, well-dispersed pruned triangular plasmonic gold nanoparticles (AuNPs) of mean size 16.4 ± 7.3 nm were prepared in Rose Bengal dye (RBD) using pulsed laser ablation in liquid method at laser fluence of 7.9 ± 0.3 J/cm 2 . These stable RBD molecules-decorated AuNPs (RBD-AuNPs) showed enhanced fluorescence (lifetime decay ranged from 7.1 ± 0.9–6.4 ± 0.2 ns) and localized surface plasmon resonance absorption. The fabricated RBD-AuNPs-coated fiber-optic relative humidity sensor (FO-RHS) when tested against polyvinyl alcohol (PVA) at intensity modulation of 40–100 % RH) displayed higher sensitivity (0.08 a.u./%RH) and linearity (0.86 a.u./%RH) compared to the one coated with pure AuNPs. This improvement was mainly due to the adherence mechanism of –OH and COOH functional groups of RBD onto AuNPs surface, enabling in binding strongly the PVA molecules via hydrogen bonds. • Gold nanoparticles (AuNPs) were made in rose Bengal dye (RBD) medium by PLAL method. • These RBD-AuNPs showed improved fluorescence and LSPR absorption. • Fluorescence lifetime decay was varied from 7.1 to 6.4 ns. • Presence of –OH and –COOH groups on AuNPs surface enabled strong binding of PVA molecules by hydrogen bonding. • RBD-AuNPs-coated fiber-optic relative humidity sensor (FO-RHS) showed fast response. • Obtained FO-RHS displayed a good sensitivity (0.08 %) and linearity (0.86 %).

Lignin-containing fibers extraction and hydrogel preparation for fiber-optic relative humidity sensor fabrication

Herein, a physicochemical pretreatment method, namely, a combination of recyclable acid hydrotrope (p-toluenesulfonic acid, p-TsOH) treatment and ultrasonic treatment (10 s), was employed to extract lignin-containing fibers (LFs) from wood material (poplar). The LFs were used to produce reinforced polyvinyl alcohol (PVA) hydrogels via a dissolution-regeneration process in LiBr⋅3H2O solution. After coating the produced hydrogel on the end face of a single-mode fiber (SMF), a fiber-optic relative humidity sensor (FORHS) was fabricated to monitor environmental humidity. A high sensitivity (4.7 dB) and good repeatability (R2 = 0.98, the confidence factor) were found within a humidity range from 45 % to 80 %. Therefore, this study provides a sustainable approach for valorization of lignocellulosic biomass.

An Easily Fabricated High Performance Fabry-Perot Optical Fiber Humidity Sensor Filled with Graphene Quantum Dots.

An easily fabricated Fabry-Perot optical fiber humidity sensor with high performance was presented by filling Graphene Quantum Dots (GQDs) into the Fabry-Perot resonator, which consists of two common single mode optical fibers. The relative humidity sensing performance was experimentally investigated by an interference spectrum drift between 11 %RH to 85 %RH. 0.567 nm/%RH sensitivity and 0.99917 linear correlation were found in experiments that showed high sensitivity, good and wide-range linear responding. Meanwhile, its good responding repeatability was demonstrated by two circle tests with increasing and decreasing relative humidity. For investigating the measurement influence caused by a temperature jitter, the temperature responding was experimentally investigated, which showed its linear responding with 0.033 nm/°C sensitivity. The results demonstrate the humidity sensitivity is greatly higher than the temperature sensitivity. The wavelength shift influence is 0.0198 nm with 0.6 °C max temperature jitter in the experiment, which can be ignored in humidity experiments. The fast-dynamic responses at typical humidity were demonstrated in experiments, with 5.5 s responding time and 8.5 s recovering time. The sensors with different cavity lengths were also investigated for their humidity response. All sensors gave good linear responding and high sensitivity. In addition, the relation curve between cavity length and response sensitivity also had good linearity. The combination of GQDs and single mode optical fibers showed easy fabrication and good performance for an optical fiber relative humidity sensor.

An optical fiber relative humidity sensor based on hollow-core fiber and hydroxypropyl methylcellulose hydrogel film

Hydroxypropyl methylcellulose (HPMC) is a kind of water-soluble polymer material. The hydrogel formed by HPMC swelling in water is a polymer network system with a netlike cross-linked structure and it can absorb lots of water if it exposed to the water environment. Therefore, an optical fiber Fabry-Perot interferometer (FPI) relative humidity (RH) sensor based on hollow-core fiber (HCF) and HPMC hydrogel film is proposed and demonstrated. The experimental results show that the proposed sensor has a binomial humidity response and 2.25 s response time in the range of 40%–99%RH. The HPMC hydrogel with hydrophilicity, natural grid-like nanostructure and biocompatibility is an effective humidity-sensitive material for optical fiber RH sensor and has great application potential in various fields.

A high-sensitivity optical fiber relative humidity sensor based on microsphere WGM resonator

Abstract In this paper, we proposed and experimentally demonstrated a high-sensitivity optical fiber relative humidity (RH) sensor, which consists of a tapered fiber and a silica microsphere resonator, for excitation of Whispering Gallery Modes (WGMs). Whispering gallery modes in the microsphere (200 µm) resonator are excited by evanescent coupling using the tapered fiber with ∼2.1 µm waist diameter. The variation of surrounding RH will induce the effective refractive index and coupling efficiency of the microsphere change, and result in transmission spectra change finally. Studies of the RH response sensitivity, the repeatability, long-term stability and temperature dependence of the proposed sensor are carried out. The sensitivity achieved in our experiments was 0.11 dB/%RH in the RH range from 20% to 70%, and 0.21 dB/% RH in the RH range from 70% to 90%. The proposed sensor with the advantages of compact size, high sensitivity, low hysteresis, good repeatability, and low cross sensitivity to temperature has good application prospects.

Reversible and Fast Responsive Optical Fiber Relative Humidity Sensor Based on Polyelectrolyte Self-Assembly Multilayer Film

A high-performance fiber-optic relative humidity (RH) sensor was prepared by layer-by-layer self-assembly of polycation, poly (4-vinylpyridinium chloride), and polyanion, sodium alginate, on the surface of a thin-core fiber modal interferometer. The process of layer-by-layer self-assembly was monitored by UV-vis spectroscopy and surface profilometer. The morphology of the fabricated multilayer film was characterized by atomic force microscopy and field emission scanning electron microscopy. A fast, reversible, and linear response to RH with a high resolution of 0.1 nm/1% RH has been experimentally demonstrated by the proposed fiber-optic sensor.

Fiber optic relative humidity sensor based on the tilted fiber Bragg grating coated with graphene oxide

A fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented. Amplitudes of the cladding mode resonances of the TFGB varies with the water sorption and desorption processes of the GO film, because of the strong interactions between the excited backward propagating cladding modes and the GO film. By detecting the transmission intensity changes of the cladding mode resonant dips at the wavelength of 1557 nm, the maximum sensitivity of 0.129 dB/%RH with a linear correlation coefficient of 99% under the RH range of 10–80% was obtained. The Bragg mode of TFBG can be used as power or wavelength references, since it is inherently insensitive to RH changes. In addition, the proposed humidity sensor shows a good performance in repeatability and stability.

Optical fiber relative-humidity sensor with evaporated dielectric coatings on fiber end-face

An optical fiber relative-humidity sensor (OFRHS) with evaporated dielectric coatings is proposed and demonstrated. The sensitive coatings, composed of multilayers of Ti3O5 and SiO2, form an extrinsic Fabry–Perot cavity on the distal end of the multimode fiber. As the effective refractive index of the porous coatings were correlated with the change of ambient Relative-humidity (RH), which will at last result in the shift of interference fringe. By monitoring the drift of reflected interference fringe under different RH levels, the information about RH of the environment under test can be extracted. Experimental results show that the average sensitivity is 0.43nm/%RH when environmental RH changes from 1.8%RH to 74.7%RH. The proposed sensor was proved to be high repeatability, little hysteresis and especially highly sensitive to lower moisture measure.

A simple fiber-optic humidity sensor based on extrinsic Fabry–Perot cavity constructed by cellulose acetate butyrate film

A fiber-optic relative humidity sensor with an extrinsic micro Fabry–Perot cavity constructed with a thin layer of cellulose acetate butyrate coated on a fiber end is presented. Its operational principle is based on the relative-humidity-dependent wavelength shift of the interference fringes formed by Fresnel reflections from both interfaces of the thin film. Both the experimental and theoretical analyses are investigated in detail. The experimental data for relative humidity ranging from 8.8% to 88.1% are measured in the both humidification and dehumidification processes, which fits the linear equation very well with a value of R2=0.9946. As observed, it shows a high sensitivity of 0.307nm/%RH with a high resolution of 0.06%. The time-dependent response of the sensor is estimated. The long term stability of the sensor is also addressed with high precision of ±0.03% over 100min. The proposed relative humidity sensor has a simple, solid, and compact structure.

Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating

In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical fiber and its expansion is reversibly affected by the change in the RH values (15.0–95.0%) of the surrounding environment, allowing an increased sensitivity (22.2 pm/%RH) and durability due to the presence of a siliceous-based inorganic component. The developed sensor was tested in a real structure health monitoring essay, in which the RH inside two concrete blocks with different porosity values was measured over 1 year. The results demonstrated the potential of the proposed optical sensor in the monitoring of civil engineering structures.

Optical fiber relative humidity sensor based on FBG incorporated thin-core fiber modal interferometer

A new fiber-optic relative humidity (RH) sensor based on a thin-core fiber modal interferometer (TCFMI) with a fiber Bragg grating (FBG) in between is presented. Poly (N-ethyl-4-vinylpyridinium chloride) (P4VP·HCl) and poly (vinylsulfonic acid, sodium salt) (PVS) are layer-by-layer deposited on the side surface of the sensor for RH sensing. The fabrication of the sensing nanocoating is characterized by using UV-vis absorption spectroscopy, quartz crystal microbalance (QCM) and scanning electron microscopy (SEM). The incorporation of FBG in the middle of TCFMI can compensate the cross sensitivity of the sensor to temperature. The proposed sensor can detect the RH with resolution of 0.78% in a large RH range at different temperatures. A linear, fast and reversible response has been experimentally demonstrated.

Optical fiber relative-humidity sensor with polyvinyl alcohol film.

We describe a fiber-optic relative-humidity (RH) sensor comprising a moisture-sensitive overlay on a single-mode side-polished fiber. The hygroscopic polymeric material deposited was polyvinyl alcohol (PVA), which proved to have good adherence and stability. The film reached a fast equilibrium with atmospheric moisture (in less than 1 min), inducing changes in the output optical power of approximately 10 dB for the 70%-90% RH range. To yield a low-cost device, single-mode standard communication fibers were used; therefore all the components of the sensor can be commercial, mass-produced telecommunication devices. The experimental results obtained are consistent with the expected behavior of the system; the output power decreases because of losses in the polished region of the fiber as the refractive index of its external medium approaches the fiber core value. Because the external medium is PVA film, its refractive index changes in response to its water content.

An evanescent-wave optical fiber relative humidity sensor with enhanced sensitivity

We report a fiber optic relative humidity (RH) sensor based on the evanescent wave absorption spectroscopy using a single U-bend plastic-clad silica fiber with high dynamic range and high sensitivity. The sensor is fabricated using a CoCl 2 doped thin polymer film coated on the bare fiber core. A comprehensive study of the sensor was made in terms of performance optimization. Sensor response was investigated in terms of the chemically synthesized cladding thickness over the centrally de-cladded U-bent probe. The effect of fiber core diameter on the sensitivity was also studied and the fiber with smaller core diameter was observed to be more sensitive unlike the previously reported results. In addition, we observed that the sensor was having a very fast response to the relative humidity, and was fully reversible, repeatable with a large dynamic range.

High dynamic range fiber optic relative humidity sensor

We present a fiber optic relative humidity sensor. The sensor was fabricated by coating a thin polyvinyl alcohol/CoCl 2 film on a 200-μm core plastic-cladding fiber; the film was deposited after removing the cladding of the fiber. It was found that bending the fiber leads to drastic changes in the response behavior. The sensor was compared against a commercially available relative humidity sensor and was found to be sensitive to relative humidity ranging from 3 to 90%. The sensor response is usually very fast, but varies at different humidity levels and has a good dynamical range. The sensor response is repeatable and fully reversible, and should be useful for monitoring relative humidity in harsh industrial environments.