Optical Fiber Hydrogen Research Articles

Optical Fiber Hydrogen Sensor Based on π-Phase-Shifted Grating and Sputtered Pd/Hf Composite Film

A novel optical fiber hydrogen sensor based on the π-phase-shifted grating and partial coated Pd/Hf composite film is proposed and experimentally demonstrated in this paper. The hydrogen sensitive Pd/Hf film with the length of 4 mm is successfully deposited in the π-phase-shifted grating region by the magnetron sputtering process and rotating fixture technology. Since the hydrogen sensitivity between the notch and flank wavelengths of the π-phase-shifted grating is different due to the partial coating only on the π-phase-shifted grating region, the relative shift between the notch and flank wavelengths is employed to characterize the hydrogen concentration in this paper. The hydrogen calibration results show that the sensor shows the good response and repeatability. At the temperature of 20 °C and the hydrogen concentration of 2%, the wavelength distance shifts of 200 nm and 500 nm Pd/Hf coatings are 12.6 pm and 33.5 pm, respectively.

Sensitivity enhanced fiber-optic hydrogen sensor based on Vernier effect of polymer-air cascaded FPI

Sensitivity enhanced fiber-optic hydrogen sensor based on Vernier effect of polymer-air cascaded FPI

Temperature-compensated fiber optic hydrogen sensing with an in-fiber Fabry-Perot etalon and a Pd:Ni-coated cavity

Temperature-compensated fiber optic hydrogen sensing with an in-fiber Fabry-Perot etalon and a Pd:Ni-coated cavity

(Invited) Development of Fiber-Optic Hydrogen Sensor Using Platinum-Supported Tungsten Trioxide-Silica Composite Film

Hydrogen has been attracting attention in recent years as a clean energy carrier that can be easily obtained by converting water into hydrogen by using various renewable natural energy resources and enable to generate energy through chemical reaction without emitting pollutants. While it has these advantages, hydrogen gas is characterized by two dangerous properties: low ignition energy and wide combustion range. Furthermore, leakage of hydrogen is difficult to detect because of its properties such as colorless, transparent, and odorless. Therefore, a leakage detection system is indispensable for the safe handling of large amounts of hydrogen energy carrier. So far, various high-performance sensors have been proposed and practically utilized. However, developments of sensor devices which can be operated at room temperature are still challenge. Furthermore, there are significant needs for distributed measurements for leakage detection of large-scale hydrogen infrastructure. In this study, fiber-optic techniques that can easily and inexpensively capture hydrogen leakage in a wide spatial area are focused to realize a line-type hydrogen sensor. In order to develop such kind of fiber optic hydrogen sensor, platinum-supported tungsten oxide film and tungsten-silica composite film were utilized as hydrogen-sensitive materials whose optical properties are significantly change through the reaction with hydrogen. A plastic-clad quartz core fiber with a core diameter of 200 μm and a cladding diameter of 230 μm (H-PCF: manufactured by Sumitomo Electric Industries) was used. In order to immobilize the hydrogen-sensitive cladding, the cladding was removed using an organic solvent. Then, the hydrogen-sensitive materials were directly coated on fiber core and immobilized by calcination in air at different temperatures. The sensing mechanism is based on the evanescent field interaction in the hydrogen sensitive clad region. As a first step, transmission spectra of sensing film itself under air and hydrogen atmosphere were evaluated for optimizing wavelength of the light source used in the sensor system. The transmittance of the sensitive film decreased in the range of wavelengths above about 500 nm after exposure to pure hydrogen, and the decrease at 1300 nm was greater than that at 850 nm, suggesting that the 1300 nm wavelength is more likely to extract changes in optical properties caused by the response (Fig. 1). Then, fiber optic sensor device was fabricated, and the amount of propagating light was measured using LED light sources at wavelengths of 850 nm and 1300 nm. In the case of using the light source with a wavelength of 1300 nm, the light attenuation rate with respect to the hydrogen response was nearly twice and the response speed was faster, compared with those at 850 nm. Therefore, it was concluded that a light source with a wavelength of 1300 nm for measurement of propagating light intensity is suitable for monitoring hydrogen leakage. Figure 1

Pd/PMMA Nanocomposite-Coated Optical Fiber Hydrogen Sensor Operating at Room Temperature With Humidity Tolerance

Pd/PMMA Nanocomposite-Coated Optical Fiber Hydrogen Sensor Operating at Room Temperature With Humidity Tolerance

Ultrafast and Reproducible Fiber-Optic Hydrogen Sensor via a Tilted Fiber Grating With Pd/WO3 Nanocoating

Hydrogen, a high-density and clean energy, has been widely used in various critical applications. However, the safety risk caused by hydrogen leakage during storage and transportation is still a non-negligible issue. Therefore, it is necessary to offer hydrogen sensors with fast response and high repeatability, and it will be perfect for achieving in situ monitoring over the lifecycle of hydrogen production and utilization. Here, we propose a compact optical fiber sensor with a short section of the tilted Bragg fiber grating (TFBG) inscribed in the fiber core and a palladium and tungsten trioxide (Pd/WO3) combined film of 40 nm thickness over the fiber surface. The TFBG excites tens of narrow cladding resonances, part of which possess refractive indexes matching that of the Pd/WO3 coating and providing the high sensitivity to the surrounding hydrogen concentration change. The sensor offers improved sensing characteristics, including the fast response time (less than 10 s), high repeatability (over tens of measurement), and excellent linear response (higher than 99.6%) over the 0% to 3% concentration range.

(Invited) Development of Fiber-Optic Hydrogen Sensor Using Platinum-Supported Tungsten Trioxide-Silica Composite Film

A fiber-optic hydrogen gas sensor using a platinum-supported tungsten oxide-silica composite film was fabricated. This sensor utilizes the absorption of the evanescent field interaction in the hydrogen sensitive clad which was composed of WO3 and SiO2, coated on a silica core with sol-gel process. As a first step, transmission spectra of sensing film itself were measured. The transmittance of the sensitive film decreased in the range of wavelengths above about 500 nm after exposure to pure hydrogen, and the change in transmittance at 1300 nm was greater than that at 850 nm. Then, fiber optic sensor device was fabricated, and the amount of propagating light was measured. In the case of using the light source with a wavelength of 1300 nm, the sensitivity with respect to the hydrogen response was nearly twice and the response speed was faster, compared with those at 850 nm.

Improved performance of a fiber-optic hydrogen sensor based on a controllable optical heating technology.

A novel, to the best of our knowledge, and compact fiber-optic hydrogen sensor based on light intensity demodulation and controllable optical heating technology is proposed and experimentally investigated. This system employs three photodetectors for optic signal transformation. The first PD is used to receive a little fraction of the amplified spontaneous emission (ASE) for calibration, and the second PD is utilized to detect optic signal reflected by a single mode fiber deposited with WO3-Pd2Pt-Pt composite film. The last PD is utilized to receive the optical power reflected by the short fiber Bragg grating (SFBG) with a central wavelength located in a steep wavelength range (the intensity decreases approximately linearly with the increase of the wavelength) of the ASE light source. A 980 nm laser and proportion integration differentiation (PID) controller were employed to ensure the hydrogen sensitive film working at an operating temperature of 60°C. This sensing system can display a quick response time of 0.4 s toward 10,000 ppm hydrogen in air. In addition, the detection limit of 5 ppm in air can be achieved with this sensing system. The stability of this sensor can be greatly enhanced with a controllable optical heating system, which can greatly promote its potential application in various fields.

Pd–Ta alloy films hydrogen sensors based on partially coated π -phase-shifted FBG

A fiber-optic hydrogen sensor based on Pd–Ta alloy films partially coated π-phase-shifted fiber-Bragg grating (FBG) is proposed and experimentally demonstrated. Three types of Pd–Ta alloy films with different Ta content were prepared via co-sputtering technology. Material characterization shows the transformation of Pd–Ta alloy to amorphous phase with the increase of Ta content, and the phase transition between α-PdTaHx and β-PdTaHx is inhibited at 2 % hydrogen concentration. Hydrogen sensing experiments show that in-situ temperature compensation is possible with Pd/Ta films partially coated on π-phase-shifted FBG. Moreover, the sensor's hysteresis phenomenon was eliminated with an increase in Ta content due to the first-order phase transition. Pd–Ta alloy films hydrogen sensor with a Ta content of 27 % is capable of in-situ temperature compensation, fast response, good stability, and reliability.

Spectroscopic Techniques and Hydrogen-Sensitive Compounds: A New Horizon in Hydrogen Detection.

Detecting hydrogen leaks remains a pivotal challenge demanding robust solutions. Among diverse detection techniques, the fiber-optic method distinguishes itself through unique benefits, such as its distributed measurement properties. The adoption of hydrogen-sensitive materials coated on fibers has gained significant traction in research circles, credited to its operational simplicity and exceptional adaptability across varied conditions. This manuscript offers an exhaustive investigation into hydrogen-sensitive materials and their incorporation into fiber-optic hydrogen sensors. The research profoundly analyzes the sensor architectures, performance indicators, and the spectrum of sensing materials. A detailed understanding of these sensors' potentials and constraints emerges through rigorous examination, juxtaposition, and holistic discourse. Furthermore, this analysis judiciously assesses the inherent challenges tied to these systems, simultaneously highlighting potential pathways for future innovation. By spotlighting the hurdles and opportunities, this paper furnishes a view on hydrogen sensing technology, particularly related to optical fiber-based applications.

Quasi-distributed optical fiber hydrogen leakage detecting system based on bus chain topology structure

Micro-mirror optical fiber hydrogen sensors have the advantages of compact structure and fast demodulation speed. All-optical sensor networks consisting of micro-mirror optical fiber hydrogen sensors are essentially necessary across the hydrogen value chain. A bus chain topology structure hydrogen leakage detecting system based on micro-mirror sensors is proposed and experimentally demonstrated. A compensating optical path with constant power supply is introduced, and the power dissipation scheme is theoretically and experimentally proposed by designating the splitting ratios of the splitters array. By constructing such a network with twenty micro-mirror hydrogen sensors, the system has been experimentally verified with good repeatability and stability under different concentrations of hydrogen. By employing this bus chain topology strategy, a quasi-distributed optical fiber hydrogen leakage detection system with micro-mirror hydrogen sensors array is realized. It will provide a promising solution with high feasibility on multi-point leakage detecting in hydrogen infrastructures.

Ultrafast and Repeatable Optical Fiber Hydrogen Sensor With Urchin-Like Nanospheres Functionalization

Ultrafast and Repeatable Optical Fiber Hydrogen Sensor With Urchin-Like Nanospheres Functionalization

Sensitive and Repeatable Optical Fiber Hydrogen Sensors Using Plasma-induced Oxygen Vacancies Magnetron Sputtering Coating Technique

Sensitive and Repeatable Optical Fiber Hydrogen Sensors Using Plasma-induced Oxygen Vacancies Magnetron Sputtering Coating Technique

Highly sensitive fiber grating hydrogen sensor based on hydrogen-doped Pt/WO3

Hydrogen sensors are key to the emerging clean hydrogen economies and fiber-optic hydrogen sensors play a unique role owing to their inherent safety and high sensitivity. Currently Pt/WO3 has been employed as the mainstream hydrogen-sensitive material in high performance hydrogen sensors. Here we develop an ultrasensitive fiber-optic hydrogen sensor with fast response by coating pretreated Pt/WO3 nanomaterial on fiber Bragg grating. We observe a great enhancement in sensitivity by the hydrogen-doping of the Pt/WO3 nanomaterials. The generation of HxWO3 composite material is confirmed by XRD, FTIR and Raman analysis. Compared with pure Pt/WO3, a 184-fold improvement in sensitivity is achieved by hydrogen doping, with a fast response of 25 s. An impressive limit of detection (LOD) of 30 ppm is demonstrated by employing both the narrowband weak FBGs and the hydrogen-doped Pt/WO3. The immunity to ambient temperature fluctuation is demonstrated by self-calibration through detecting the wavelength difference between a pair of FBGs. Good specificity is also demonstrated. This technology shows great potential in high spatial-resolution quasi-distributed hydrogen sensing.

Review of the Status and Prospects of Fiber Optic Hydrogen Sensing Technology

With the unprecedented development of green and renewable energy sources, the proportion of clean hydrogen (H2) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible, high-performance H2 sensors to detect and monitor hydrogen concentration are essential. This review discusses a variety of fiber-optic-based H2 sensor technologies since the year 1984, including: interferometer technology, fiber grating technology, surface plasma resonance (SPR) technology, micro lens technology, evanescent field technology, integrated optical waveguide technology, direct transmission/reflection detection technology, etc. These technologies have been evolving from simply pursuing high sensitivity and low detection limits (LDL) to focusing on multiple performance parameters to match various application demands, such as: high temperature resistance, fast response speed, fast recovery speed, large concentration range, low cross sensitivity, excellent long-term stability, etc. On the basis of palladium (Pd)-sensitive material, alloy metals, catalysts, or nanoparticles are proposed to improve the performance of fiber-optic-based H2 sensors, including gold (Au), silver (Ag), platinum (Pt), zinc oxide (ZnO), titanium oxide (TiO2), tungsten oxide (WO3), Mg70Ti30, polydimethylsiloxane (PDMS), graphene oxide (GO), etc. Various microstructure processes of the side and end of optical fiber H2 sensors are also discussed in this review.

Fiber-optic hydrogen concentration sensor based on the Fabry–Perot interferometer, fabricated using nanoscale layers of Al2O3/Ta/SiO2

The article discusses the technological and operational characteristics of a fiber-optic sensor of molecular hydrogen concentration based on the Fabry–Perot interferometer. The possibility of registering the hydrogen concentration by deformation of a membrane with an Al2O3/Ta/SiO2 layer deposited on its outside surface is shown. The deposited α-tantalum film provides high diffusion of hydrogen, and allows you to create sensors with a fast response to hydrogen, less than 10s. The almost complete absence of cross-sensitivity of the sensor to temperature in the range from 20 °C to 80 °C at a hydrogen pressure of 1 atm.

Improved performance of fiber-optic hydrogen sensor of porous Pt/WO3 based on ZIF-8

A novel fiber-optic hydrogen sensor including Pt/WO3 sensing material with a microporous structure is proposed and experimentally demonstrated with improved performance. The proposed Pt/WO3 sensing material is realized by introducing metal-organic frameworks (MOFs) as templates. The mesoporous structure of the ZIF-8 template improves the reactive sites of hydrogen sensitive materials with hydrogen. Hydrogen sensors were fabricated by combining the synthesized material with Fiber Bragg Gratings (FBGs) and the performance of hydrogen sensors was investigated. The experimental results show that the hydrogen sensitivity of the FBG with ZIF-8 synthesized Pt/WO3 has been increased to 0.075 pm/ppm, which is twice that without ZIF-8 synthetization. The stability and the response speed are also significantly improved. The introduction of microporous MOFs templates into Pt/WO3 sensing material will greatly accelerate the wide application of Pt/WO3-based fiber optic hydrogen sensors on hydrogen leakage detection.

A Review of Hydrogen Sensors for ECLSS: Fundamentals, Recent Advances, and Challenges

The development of hydrogen sensors with high detection accuracy, fast response times, long calibration periods, and good stability has become the focus of the space station environmental control and life support subsystem. We analyze the current research status of different types of hydrogen sensors, including catalyst combustion type, heat conduction type, semiconductor type, fiber optic type, etc. The response signals of most hydrogen sensors are affected by temperature and humidity, resulting in cross-sensitivity. Reducing the cross-sensitivity of temperature, humidity, and other interfering factors to achieve accurate hydrogen measurement in different environments is a challenge that limits the development of hydrogen sensors. Several hydrogen sensors that are currently commercially available have a narrow operating temperature range, most of them can only measure at room temperature, and high-temperature environments require a higher accuracy and lifetime of the sensor than required at room temperature. Many new hydrogen-sensitive materials were developed to improve the performance of the sensors. The excellent performance of fiber-optic hydrogen sensors is beneficial to temperature compensation and distributed multiparameter measurement, as well as to the research and development of intelligent sensing systems, in the context of the Internet of Things. The signal detection and demodulation techniques of fiber-optic sensors are the focus of future hydrogen sensor research.

Multi-point optical fiber hydrogen detection system based on light polarization modulation

A hydrogen sensing system including 8 sensors based on light polarization modulation is developed and demonstrated for simultaneous multi-point hydrogen sensing with high sensitivity. Each sensor is composed of a polarizer, a polarization control, and a short segment of polarization maintaining fiber (PMF) coated with Pt-loaded WO3. Due to the exothermic reaction between hydrogen and WO3 with the help of catalyst Pt, the local temperature of PMF increases and the reflective spectrum of the sensor shift accordingly. The self-developed control system software achieves the sequential scanning and recording of the reflection spectra of each sensor by programable controlling a light switch, and then gives the measured hydrogen concentration of each channel in real-time according to the spectrum shift by using an automatic dip finding algorithm with Gaussian fitting. The experimental results show that the proposed type of sensor has ultra-high hydrogen sensitivity, with a maximum value of −20.22 nm/% (vol %); packaging with foam substrate helps to reduce the response time of the device; the hydrogen sensor is almost unaffected by environmental relative humidity. Moreover, the hydrogen sensing system is experimentally proved having good stability and repeatability.

Fiber-tip Fabry-Pérot interferometer with a graphene-Au-Pd cantilever for trace hydrogen sensing.

The widespread utilization of hydrogen energy has increased the demand for trace hydrogen detection. In this work, we propose a fiber-optic hydrogen sensor based on a Fabry-Pérot Interferometer (FPI) consisting of a fiber-tip graphene-Au-Pd submicron film cantilever. The palladium (Pd) film on the cantilever surface is used as hydrogen-sensitive material to obtain high sensing sensitivity. Hydrogen sensing is realized by monitoring the resonant frequency shift of the FPI introduced by the interaction between Pd film and hydrogen molecules. The hydrogen sensor is proven for low-hydrogen-concentration detection with hydrogen concentrations in the range of 0-1000 ppm, and experimentally characterized by a highest sensitivity of 30.3 pm ppm-1 in a low hydrogen concentration of 0-100 ppm, which is more than two orders higher than for previously reported FPI-based sensors. In real-time hydrogen monitoring, a rapid reaction time of 31.5 s was achieved. This work provides a compact all-optical solution for the safe detection of low hydrogen concentrations, which is an interesting alternative for trace hydrogen detection in the aerospace industry, energy production, and medical applications.