Gaopeng Wang

Self-compensated microstructure fiber optic sensor to detect high hydrogen concentration

Dual-cavity microstructure fiber optic hydrogen sensor based on evaporated Pt/WO(3) film was proposed and experimentally explored in this paper, which provides a novel solution to detect high hydrogen concentration (10-30% H(2)). Dual-cavity microstructure fabricated by splicer is composed of an inner air-cavity and a collapsed photonic crystal fiber cavity. The proposed sensor has the advantages of miniature structure, stable configuration, low cost. Based on three-beam interference model and verification experiments, the compensation function to the fluctuation of light source and fiber loss is proved from the theoretical simulation and experimental investigation. The sensor has a short response time (1min), good repeatability and reliability. Besides, the change of temperature affects the response value of the hydrogen sensor, but the impact can be neglected in 10-30% H(2).

Fiber Bragg grating sensors with Pt-loaded WO3 coatings for hydrogen concentration detection down to 200?ppm

A novel fiber optic hydrogen sensor was proposed and experimentally demonstrated. The sensing element was a fiber Bragg grating (FBG) covered with Pt-loaded WO3 coating annealed at 315 °C for 1 h. At room temperature of 25 °C, the FBG hydrogen sensor has 448 pm wavelength shift toward 8000 ppm hydrogen, and it can detect hydrogen as low as 200 ppm. Experimental results show that ambient humidity has little effect on the performance of the FBG hydrogen sensor, whereas the sensitivity of the FBG hydrogen sensor will be decreased at lower ambient temperatures. The relationship between the wavelength shift of the proposed sensor and hydrogen concentration is proposed and discussed in this article.

Optical Fiber Grating Hydrogen Sensors: A Review

In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests due to their good reliability and distributed measurements. This review paper mainly focuses on optical fiber hydrogen sensors associated with fiber gratings and various materials. Their configurations and sensing performances proposed by different groups worldwide are reviewed, compared and discussed in this paper. Meanwhile, the challenges for fiber grating hydrogen sensors are also addressed.

Water photolysis effect on the long-term stability of a fiber optic hydrogen sensor with Pt/WO 3

One of the technological challenges for hydrogen sensors is long-term stability and reliability. In this article, the UV-light irradiation was introduced into the hydrogen sensing process based on water photolysis effect of Pt/WO3. Ascribing to that, fiber optic hydrogen sensor with Pt/WO3 nanosheets as the sensing element was demonstrated with significantly improved performance of stability. Under UV irradiation, the hydrogen sensor exhibits higher sensitivity and resolution together with a smaller error range than that without UV irradiation. The enhanced performance could be attributed to the effective decomposition of water produced in the hydrogen sensing process due to the water photolysis effect of Pt/WO3. The influence of the water on stability was evaluated using experimental results, and the UV irradiation to remove water was analysed by theoretical and FT-IR spectra. This work provides new strategy of UV-light irradiation to promote the long-term stability of hydrogen sensor using Pt/WO3 as the sensing element.

Novel polyimide coated fiber Bragg grating sensing network for relative humidity measurements.

A novel relative humidity (RH) sensing network based on ultra-weak fiber Bragg gratings (FBGs) is proposed and demonstrated. Experiment is demonstrated on a 5 serial ultra-weak FBGs sensing network chopped from a fiber array with 1124 FBGs. Experimental results show that the corresponding RH sensitivity varies from 1.134 to 1.832 pm/%RH when ambient environmental RH changes from 23.8%RH to 83.4%RH. The low-reflectance FBGs and time-division multiplexing (TDM) technology makes it possible to multiplex thousands of RH sensors in single optical fiber.

Ultra-high sensitive optical fiber hydrogen sensor using self-referenced demodulation method and WO 3 -Pd 2 Pt-Pt composite film

A novel fiber optic hydrogen concentration detection platform with significantly enhanced performance is proposed and demonstrated in this paper. The hydrogen sensing probe was prepared by depositing WO3-Pd2Pt-Pt composite film on the fiber tip of two Bragg gratings paired with high-low reflectivity. At a room temperature of 25°C, the hydrogen sensor has a significant response towards 10 ppm hydrogen in nitrogen atmosphere, and may detect tens of ppb hydrogen changes when the hydrogen concentration is between 10~60 ppm. Besides, the proposed system shows quick response when the hydrogen concentration is above 40 ppm. Moreover, the hydrogen sensor shows good repeatability during the hydrogen response. This work proposes a new concept to develop hydrogen sensing technology with ultra-high sensitivity, which can significantly promote its potential application in various fields, especially for ultra-low hydrogen detection in oxygen-free environment.

Ultra-Weak Fiber Bragg Grating Sensing Network Coated with Sensitive Material for Multi-Parameter Measurements

A multi-parameter measurement system based on ultra-weak fiber Bragg grating (UFBG) array with sensitive material was proposed and experimentally demonstrated. The UFBG array interrogation principle is time division multiplex technology with two semiconductor optical amplifiers as timing units. Experimental results showed that the performance of the proposed UFBG system is almost equal to that of traditional FBG, while the UFBG array system has obvious superiority with potential multiplexing ability for multi-point and multi-parameter measurement. The system experimented on a 144 UFBG array with the reflectivity of UFBG ~0.04% for the four target parameters: hydrogen, humidity, temperature and salinity. Moreover, a uniform solution was customized to divide the cross-sensitivity between temperature and other target parameters. It is expected that this scheme will be capable of handling thousands of multi-parameter sensors in a single fiber.

Fiber Optic Sensors Based on Nano-Films

The combination of fiber optics with sensitive nano-films offers great potential for the realization of novel sensing concepts. Miniatured optical fiber sensors with thin films as sensitive elements could enable new fields of optical fiber sensor applications. Thin films work as sensitive elements and transducer to get response and feedback from environments, while optical fibers are employed to work as signal carrier. In this chapter fiber optic sensors based on nano-films are reviewed.

Optic fiber hydrogen sensor based on high-low reflectivity Bragg gratings and WO3-Pd-Pt multilayer films

A novel optic fiber hydrogen sensor is proposed in this paper. Two Bragg gratings with different reflectivity were written in single mode fiber with phase mask method by 248 nm excimer laser. The end-face of singe mode fiber was deposited with WO3-Pd-Pt multilayer films as sensing element. The peak intensity of low reflectivity FBG is employed for hydrogen characterization, while that of high reflectivity FBG is used as reference. The experimental results show the hydrogen sensor still has good repeatability when the optic intensity in the fiber is only 1/3 of its initial value. The hydrogen sensor has great potential in measurement of hydrogen concentration.

Pt nanoparticles encapsulated in mesoporous tungsten oxide to enhance the repeatability of a FBG hydrogen sensor

Mesoporous WO3 is synthesized by using SBA-15 and KIT-6 silica as templates, and Pt nanoparticles are then incorporated into the mesochannels of mesoporous WO3. TEM and BET results demonstrate the existence of the pore structure. Hydrogen sensing tests show that the repeatability of the sensors based on mesoporous WO3 has been significantly improved by an order of magnitude. Based on XRD, TEM and Raman spectrum results, a model of Pt nanoparticles encapsulated into channels of mesoporous WO3 is proposed to explain the improved repeatability of mesoporous WO3.