High-sensitivity Fiber Research Articles

High sensitive triangular photonic crystal fiber sensor design applicable for gas detection

A new triangular photonic crystal fiber with a based microstructure core gas sensor has been proposed for the wavelength range from 1.1μm to 1.7μm. The guiding trait of the proposed structure depends on geometric parameters and wavelength, which are numerically studied by the finite element method. According to the results, the relative sensitivity obtained as high as 75.14% at 1.33μm wavelength. high birefringence and effective area are also obtained by order of 3.75×10-3 and 14.07 μm2 finally, low confinement loss of 1.41×10-2 dB/m is acquired at the same wavelength. The variation of the diameters in the cladding and core region is investigated and the results show that this structure has good stability for manufacturing goals. Since the results show the highest sensitivity at wavelengths around 1.2μm to 1.7μm, which is the absorption line of many gases such as methane (CH4), hydrogen fluoride (HF), ammonia (NH3), this gas sensor can be used for medical and industrial applications.

High-sensitivity fiber optic magnetic field sensor based on lossy mode resonance and hollow core-offset structure

An optical fiber magnetic field sensor based on lossy mode resonance (LMR) was designed. Furthermore, a hollow core-offset structure was designed to enhance the performance. Due to the destruction of the circular symmetry structure, the sensor has strong birefringence, resulting in x-polarization and y-polarization with two independent resonance valleys. The refractive index changes from 1.358 to 1.390 and a high sensitivity of 11,483.12 nm/RIU was obtained. In addition, the influence of structural parameters on the sensor was investigated. Magnetic field sensitivities of 893 pm/Gs and 754 pm/Gs were obtained theoretically. The feasibility of LMR is demonstrated for magnetic field measurements and a reference is provided for an optical fiber magnetic field.

High sensitivity and resolution sensor plastic optical fiber for determining compressive and tensile tensor concrete applications

This research discusses sensors based on plastic optical fiber (POF) for concrete compressive tests and concrete tensile tests. Sensors are made of plastic optical fibers without coat attached to concrete surfaces or planted in concrete with straight, one bending, and two bending configurations. Sensors are attached to concrete with four configurations to find the best sensitivity and resolution values. The pressure on the sensor is related to the loss of power. The best sensor characteristic based on plastic optical fiber for concrete compressive test and the concrete tensile test is the sensor with two bending configurations that are planted in concrete. The sensitivity and resolution values in the concrete compressive strength test were 0.085 volts/kN and 0.047 kN. While the value of sensitivity and resolution of the concrete tensile test obtained is 0.082 volts/kN, and 0.048 kN. Sensor-based on plastic optical fiber has the advantage that is low cost and simple in measurement method that can be applied for monitoring the condition of the building structure.

High Sensitive Fiber Optic Microphone with Micro-Electro-Mechanical System Corrugated Diaphragm

High Sensitive Fiber Optic Microphone with Micro-Electro-Mechanical System Corrugated Diaphragm

基于游标效应的高灵敏光纤温度和应变传感器

基于游标效应的高灵敏光纤温度和应变传感器

High-Sensitivity D-Shaped Fiber Sensor Based on a Large-Hole Self-Reference Channel for Glucose Aqueous Solution

In this work, we design a D-shaped photonic-crystal fiber (PCF) sensor with a large-hole self-reference channel based on the surface plasmon resonance. Using the numerical calculation method, we study variations of the transmission spectrum with concentration for the aqueous glucose solution. By optimizing the silver-film thickness of the reference and detected channels, we find that the sensitivity does not depend on the silver-film thickness h of the self-reference channel at high glucose concentrations. The sensitivity is more influenced by the silver-film thickness H of the detected channel. Finally, we obtain the maximum sensitivity of the D-shape PCF sensor equal to 20.2 nm/(mg/ml) and the lower limit of detection equal to 2.5 μg/ml at the silver-film thickness of the detected channel H = 50.0 nm and the self-reference h = 40.0 nm.

Fiber Bragg Grating Sensor Based Vibration Monitiring for Foreign Matter Invasion of Protective Barrier

A vibration monitoring system based on fiber Bragg grating is proposed to meet the need of protective barrier along the railway to monitor the foreign matter invasion. A high sensitivity fiber Bragg grating vibration sensor based on cantilever structure is developed. Three vibration sensors were deployed to a protective barrier with a length of 20 meters to conduct intrusion vibration monitoring test. Test results show that: 1) the fiber Bragg grating vibration sensor can well monitor the vibration signal; 2) the vibration intensity decreases obviously with the distance impact position increasing; 3) the response time of vibration measurement of different sensors is also in sequence when the distance impact location is different. Therefore, the magnitude of the external impact and the impact position in the protective barrier can be analyzed through the response amplitude distribution of each sensor and the response time sequence of the sensors.

Distributed Pressure Sensing Using an Embedded-Core Capillary Fiber and Optical Frequency Domain Reflectometry

In this paper, we describe a distributed pressure sensor using a simplified and high sensitive microstructured optical fiber - the embedded-core fiber - and autocorrelation analysis of the data obtained from an optical frequency domain reflectometer (OFDR). The special fiber consists of a microcapillary, which has a germanium-doped core placed within the capillary wall. When this structure is subjected to pressure variations, an asymmetric stress distribution is induced within the fiber, entailing birefringence variations. Here, we show that the use of a commercial OFDR with submillimeter resolution-together with an autocorrelation data analysis routine in the spectral domain allows mapping the fiber birefringence and performing distributed pressure sensing. In the experiments, the fiber passed through two pressure chambers, which allowed for pressure to be locally and independently applied. No cross-sensitivity between the pressure points was observed. The embedded-core fiber exhibited a birefringence sensitivity to pressure of 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> bar <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , which is 21% higher than that measured in commercial photonic crystal fibers using the same setup.

Broadband and High Sensitivity FBG Accelerometer Based on Double Diaphragms and h-Shaped Hinges

A novel broadband and high sensitivity fiber Bragg grating (FBG) accelerometer is designed and analyzed. The accelerometer is based on a compact structure consisting of double diaphragms and h-shaped hinges. The h-shaped hinge structure is used to break through the restriction between sensitivity and resonance frequency. The FBG accelerometer is demodulated by an interferometric method and test results show that the acceleration sensitivity is 32 dB re pm/g between 1 Hz and 1 kHz, with a fluctuation less than ±3 dB, and the resonant frequency is above 1.6 kHz. The cross-sensitivity is less than -26 dB in the flat frequency of 15μg/√ Hz in a wide frequency range, making it promising range. The sensor shows a high acceleration resolution for cross-well seismic, micro-seismic monitoring and electromechanical equipment vibration monitoring, etc.

High Sensitivity Fiber Bragg Grating Acceleration Sensor Based on Rigid Hinge

In order to break through low sensitivity limitation of the existing fiber Bragg grating (FBG) acceleration sensor, a new high sensitivity FBG acceleration sensor based on rigid hinge is proposed. The working principle innovation is that the sensor uses the rigid body rotation motion instead of the existing elastic deformation. The novel structure is that the pendulum rotates around the rigid hinge and the structure is symmetrically designed, which increases the elongation of the fiber grating by twice. The resonance frequency and sensitivity formula of FBG acceleration sensor is theoretically obtained by analysis. The influence of size parameters of the structure on sensor sensitivity and resonance frequency is further analyzed by MATLAB, and finally the structural parameters are optimized. On the basis, the first-order natural frequency of the sensor is simulated by ANSYS Workbench17.0. Experimental studies show that the natural frequency of the acceleration sensor designed in this paper is 39 Hz, the sensitivity of the sensor is 949.2 pm/g at 15 Hz, and the cross-interference is less than 6.49%, which is suitable for precision measurement under low frequency micro-vibration.

High sensitive D-shaped photonic crystal fiber sensor with V-groove analyte channel

In this work, we propose a D-shaped photonic crystal fiber (PCF) based surface plasmon resonance sensor with a V-groove analyte channel for the detection of analytes and numerically analyze its sensing performance for a wide range of liquid analytes. In a stand out to the usual D-shaped fiber, we design a separate V-groove for holding the analyte sample, which not only minimizes the sample quantity but also reduces the metal coating region. By using the finite element method, we find that the proposed PCF sensor has a maximum wavelength sensitivity of 31,600 nm/RIU for a sensing range of 1.33–1.43 with a resolution of 3.16 × 10−6 RIU. Besides, the numerical results corroborate that the proposed sensor is robust against the variations of structural parameters. Thus, the proposed sensor is suitable for detecting biomolecules, organic and chemical samples. As the proposed sensor exhibits promising sensing performance, we envisage that the sensor could be engaged in various fields of chemical and biosensing applications.

Fiber optic Fabry–Pérot acoustic sensor using PVC and GO diaphragms

Here, a low cost high sensitive fiber optic Fabry–Pérot interferometer (FPI) acoustic sensor is developed. A novel polyvinyl chloride (PVC) diaphragm-based fiber-tip FPI is implemented for the sake of acoustic sensing with high sensitivity. The PVC diaphragm has been coated to the pigtail of a standard single-mode fiber (SMF). Subsequently, the multilayer graphene oxide (GO) is deposited on the PVC cavity. The configuration of (SMF + PVC + GO) attests a sensitivity higher than (SMF + PVC). In fact, GO acts as the acoustic membrane and PVC features as the cavity to demonstrate a sensitive FPI acoustic sensor. The results also give out the acoustic sensitivity of the (SMF + PVC + GO) sensor equivalent to 685 mV/Pa (19.9 rad/Pa) at 1 kHz and a 100 mPa pressure with a frequency response ranging 0.1–10 kHz.

High-sensitivity salinity measurement sensor based on no-core fiber

A compact, stable, low cost and high sensitivity fiber salinity sensor based on single mode fiber-single mode fiber-no-core fiber-single mode fiber-single mode fiber (SSNSS) structure is proposed and demonstrated. It is proved by experiments and simulations that the sensor has high sensitivity to external refractive index (RI) changes, so as to achieve the purpose of gauging the seawater salinity. When the RI of surrounding media in sensing area changes, the absolute value of sensitivity for the refractive index measurement can be above 16,000 nm/refractive index unit (RIU) that is higher than other fiber salinity sensors as we known. In the experimental study, a fiber salinity sensor with the sensitivity of up to -3.42 nm/‰ was achieved when the salinity varied between 0‰ and 40.001‰, and the sensor showed a good linear response.

A High-Sensitivity Fiber Bragg Grating-Based Distal Force Sensor for Laparoscopic Surgery

This paper presents a Fiber Bragg Grating (FBG)-based distal force sensor with a high sensitivity and a relatively large measurement range to provide force feedback for laparoscopic surgery. The proposed sensor design mainly consists of a force-sensitive flexure, one tightly suspended optical fiber embedded with an FBG sensing element and a contact head. The proposed flexure has been miniaturized based on improvement and optimization of a parallel structure form and a serial cantilever beam-based structure to achieve an excellent axial linear force-deformation relationship and a large measurement range. The optical fiber adopts a two-point pasting method, and has been tightly stretched and glued along the flexure’s central line to achieve improved sensitivity and avoid FBG chirping failure. Finite element method (FEM)-based simulation has been performed to investigate both static and dynamic performances of the proposed design. The simulation-enabled optimization has been implemented to achieve optimal structural parameters and enhanced sensitivity. The optimized design has been prototyped and calibrated to demonstrate an excellent linearity with a small linearity error of 0.14% and achieve a high resolution of 21mN within a measurement range of [0, 12N]. The further optimized version with the removal of small deformation constraint can reach a higher resolution of 9.3 mN within an operating range of [0, 7N]. Dynamic loading experiments have been conducted to validate the effectiveness of the proposed designs.

High temperature and vector curvature sensor with high linearity and sensitivity based on asymmetric dual-core photonic crystal fiber

A high linear sensitivity fiber temperature and vector curvature sensor based on dual-core photonic crystal fiber was designed and implemented. Theoretical and experimental results show that, the temperature sensing sensitivity at 30 °C–510 °C is 61.68 pm °C−1, and the linear fitting coefficient is up to 0.998. The sensor can realize high linear (0.997) vector bending sensing on the plane where the two cores are located, and the sensing sensitivity is 3262.57 nm mm and −1608.56 nm mm respectively. Compared with fiber sensors based on complex and fragile structures, it has higher mechanical strength, wider sensing range, and simple preparation process.

High sensitivity fiber displacement sensor based compound ring laser cavity with linear variation of beat frequency signal

A novel fiber sensor based compound ring laser cavity with linear variation of frequency is proposed and demonstrated experimentally. The compound ring laser cavity is comprised of a ring cavity and a straight cavity. This system can generate the beat frequency spectrum by employing an erbium doped fiber amplifier, a fiber Bragg grating is used as a sensor head and the straight cavity reflector, a π phase shifted fiber Bragg grating serves as a microwave photonic passband filter. The principle of the proposed sensor is theoretically analyzed, showing that as the displacement increases the beat frequency decreases, and there exists a linear relationship between displacement change and beat frequency shift. In experiment, it is shown that the sensor has a high sensitivity of about 86.19 kHz/mm and can achieve a good linear response (&lt;i&gt;R&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt; = 0.9973), and that the minimum monitored displacement is about 10 μm. The measurement results demonstrate that the sensor is accurate, sensitive, and the proposed sensor system has a compact and simple structure, which makes it convenient for more applications in future.

High-sensitivity fiber liquid crystals temperature sensor with tiny size and simple tapered structure

This Letter presents a new type of optical fiber probe used to detect temperature, whose structure is very simple. The optical fiber probe is filled with cholesteric liquid crystals (CLCs) whose reflected light varies with temperature. The experimental results show that the proposed sensor can achieve a temperature sensitivity of 5.64 nm/°C in the temperature range of 18–40°C. The sensor has the advantages of simple structure, low cost, and easy mass manufacture. Its size is very tiny (the tapered structure, 125 μm in maximum diameter and <300 μm in length) and it is easy to integrate and measure. Meantime, the tapered structure of the probe is also ideal for measuring small samples such as cells and microfluidic channels, which will be a promising candidate for monitoring temperature fluctuations in small spaces.

High sensitivity fiber sensor for measurement of Cd2+ concentration in aqueous solution based on reflective Mach-Zehnder interference with temperature calibration.

We propose a novel fiber chemical sensing system based on reflective Mach-Zehnder interference with temperature calibration for the measurement of Cd2+ in aqueous solution. The sensing system has high measurement sensitivity of Cd2+ with an estimated minimum detection limit of 4×10-7 mol/L at a spectral resolution of 0.02 nm and with long-term stability. The fiber sensing head is prepared by coating a sensing membrane on a fused tapering single-mode fiber. The thiourea group of the sensing membrane has an effective combination effect on Cd2+. Disturbance from ambient temperature fluctuation on the measurement of Cd2+ concentration can be eliminated with the fiber Bragg grating.

High-sensitivity fiber salinity sensor based on an exposed-core microstructured fiber interferometer

A high-sensitivity salinity sensor based on a free space propagation-core mode Mach–Zehnder interferometer was proposed with a well-designed exposed-core microstructured optical fiber. The real-time salinity sensing was achieved by using an exposed-core microstructured optical fiber shortened to 228 µm. The proposed sensor has a salinity measurement range from 0 ‰ to 40 ‰ and a salinity sensitivity of around −2.29 nm/‰, corresponding to a refractive index sensitivity of −13 103.16 nm/RIU. The measurement error caused by the temperature is only 0.02 ‰ °C−1, which can be neglected in practical applications. This kind of sensor also presents a Fabry-Perot interference phenomenon besides the Mach–Zehnder interferometer, which shows a flexible sensing structure. The proposed sensor offers an alternative method for accurate measurement of seawater salinity.

Modeling of a fiber optic SPR biosensor employing Tin Selenide (SnSe) allotropes

We report an unique design of a fiber optic SPR biosensor in this study utilizing two-dimensional (2D) Tin Selenide (SnSe) allotropes not revealed before. Due to enhanced optical characteristics with 2D graphene-like structure of monolayer SnSe, recently it is getting much attraction by the researchers to use as a biomolecular recognition element (BRE) in sensor design. Sensitivity of the proposed fiber optic sensor with three sorts of monolayer allotropes of SnSe (α-SnSe, δ-SnSe and ε-SnSe) as a BRE is analyzed through wavelength interrogation scheme for sensing application. Results show that sensors with α-SnSe, δ-SnSe, and ε-SnSe exhibit sensitivities of 3225 nm/RIU, 3300 nm/RIU and 3475 nm/RIU respectively. It is obvious that proposed sensor with improved sensitivity outperforms the conventional Ag-only based sensors having poor sensitivity of 1800 nm/RIU. Thus the proposed SnSe allotropes can be reasonable alternate of conventional BRE to design extremely high sensitive fiber optic SPR biosensors for DNA hybridization.