Showing papers on "Fiber Bragg grating published in 2020"

Fiber Bragg grating sensors for monitoring of physical parameters: a comprehensive review

Abstract: Fiber Bragg grating has embraced the area of fiber optics since the early days of its discovery, and most fiber optic sensor systems today make use of fiber Bragg grating technology Researchers have gained enormous attention in the field of fiber Bragg grating (FBG)-based sensing due to its inherent advantages, such as small size, fast response, distributed sensing, and immunity to the electromagnetic field Fiber Bragg grating technology is popularly used in measurements of various physical parameters, such as pressure, temperature, and strain for civil engineering, industrial engineering, military, maritime, and aerospace applications Nowadays, strong emphasis is given to structure health monitoring of various engineering and civil structures, which can be easily achieved with FBG-based sensors Depending on the type of grating, FBG can be uniform, long, chirped, tilted or phase shifted having periodic perturbation of refractive index inside core of the optical fiber Basic fundamentals of FBG and recent progress of fiber Bragg grating-based sensors used in various applications for temperature, pressure, liquid level, strain, and refractive index sensing have been reviewed A major problem of temperature cross sensitivity that occurs in FBG-based sensing requires temperature compensation technique that has also been discussed in this paper

Recent Advances and Tendency in Fiber Bragg Grating-Based Vibration Sensor: A Review

Abstract: Vibration sensing is critical to monitor and ultimately preserve the health state of engineering systems. These systems with a large structure are typically working in some harsh environments including strong magnetic fields. However, traditional electrical sensors are difficult to accurately measure the vibration under harsh environments. Besides these instinct advantages of normal fiber optic sensors (FOS) sensors such as compact size, passive sensing, resistance to electromagnetic interference, etc., fiber Bragg grating (FBG) sensors have a capability of distributed sensing based on wavelength demodulation and resistance to light intensity fluctuation and unwanted fiber bending losses. Such merits lead them to be a hot topic in FOS field and excellent candidates for vibration sensing. Three types of FBG-based vibration sensors have been classified based on the difference of vibration-strain coupling way to FBG in this survey, which are pasted FBG-based, axial property of FBG-based and transverse property of FBG-based, respectively. FBG-based vibration sensors' principles and designs have been introduced and discussed. Recent advances in the applications of FBG-based vibration sensors have been investigated. The limitations and prospects of the FBG-based vibration sensing technologies have been analyzed and discussed.

Analytical Model Analysis of Reflection/Transmission Characteristics of Long-Period Fiber Bragg Grating (LPFBG) by Using Coupled Mode Theory

Abstract: This study presents an analytical model analysis of reflection/transmission characteristics of long-period fiber Bragg grating (LPFBG) by using coupled mode theory. Reflected signal power is deeply studied against grating length at the optimum operating signal wavelength of 1550 nm for the proposed and previous models. Reflectivity and transmission coefficient are also clarified versus operating wavelength for the previous model and proposed a model with a central wavelength of 1550 nm, Δn = 0.003 and optimum grating length of 30 mm. In the same way, the reflectivity and transmission coefficient are outlined against relative refractive grating difference step at the optimum wavelength of 1550 nm and optimum grating length of 30 mm. The optimum LPFBG can be achieved with the optimum grating length of 30 mm, operating wavelength of 1550 nm and relative refractive grating difference step of 0.3 %.

Review of high sensitivity fibre-optic pressure sensors for low pressure sensing

Abstract: Fibre Bragg grating (FBG) pressure sensors show a great potential in replacing conventional electrical pressure sensors due to their numerous advantages. However, increasing their pressure sensitivity performance for low hydrostatic pressure measurement is still a challenge. This paper reviewed recent pressure sensitivity enhancement methods that could be divided into two groups, namely intrinsic and extrinsic. For the intrinsic enhancement method, this paper reviewed polymer FBGs, special fibre sensors, interferometric sensors, and special grating sensors. For the extrinsic enhancement method, polymer-based pressure transducers, diaphragm-based pressure transducers, and other structure-based pressure transducers were reviewed in detail.

Magnetic field and temperature dual-parameter sensor based on magnetic fluid materials filled photonic crystal fiber

Abstract: A dual-parameter sensor based on a photonic crystal fiber (PCF) concatenated with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. Novel magnetic fluids (MF) with different concentration and surfactant are filled in the air holes of PCF. The magnetic field measurement property is only determined by PCF, while the temperature is co-determined by PCF and FBG. Experimental results show that the wavelength shift has a good linearity corresponding with temperature and magnetic field. Temperature and magnetic field sensitivity are proportional to concentration of MF and are affected by different surfactants. For PCF point, when polyethylene glycol is used as a surfactant and the magnetic fluid concentration is equal to 0.15, the highest magnetic field sensitivity is up to 924.63 pm/mT. The proposed sensor has a high sensitivity as well as cross-sensitivity resistance, which provides a promising candidate for dual-channel filtering or multi-parameter measurement applications.

FBG Sensors for Environmental and Biochemical Applications—A Review

Abstract: Sensors play a large role in monitoring and ensuring that environmental parameters satisfy industrial requirements. They offer crucial safety measures in the early detection of hazards. Conventional electrical sensors possess several drawbacks that hinder their use in environmental sensing. Research has explored and optimized optical-based sensors because they are more robust, immune to electromagnetic interference and offer multiplexing capabilities for sensor arrays accompanied by ease of modification to cater to different measurands. Fibre Bragg grating is the perturbation of the refractive index imprinted within the core of an optic fibre via an intense UV laser. The gratings, when perturbed by external parameter changes, will induce a shift in their wavelength, indicating detection. With modifications such as hygroscopic coating and different grating profile imprinting, FBG can detect various physical and chemical parameters. Environmental, pharmaceutical and biochemical fields can benefit from FBG sensing because their parameters affect not only their product quality but also the lives of consumers. This review discusses some of the FBG sensors that have been proposed to serve in environmental and biochemical applications.

Light propagation through metamaterial temporal slabs: reflection, refraction, and special cases.

Abstract: Time-varying metamaterials are artificial materials whose electromagnetic properties change over time. Similar to a spatial medium discontinuity, a sudden change in time of the metamaterial refractive index induces the generation of reflected and refracted light waves. The relationship between the incident and emerging fields at one temporal interface has been subject of investigation in earlier studies. Here, we extend the study to a temporal slab, i.e., a uniform homogeneous medium that is present in the whole space for a limited time. The scattering coefficients have been derived as a function of the refractive indices and application time, demonstrating that the response of the temporal slab can be controlled through the application time, which acts similarly to the electrical thickness of conventional spatial slabs. The results reported in this Letter pave the way to creating novel devices based on temporal discontinuities, such as temporal matching networks, Bragg grating, and dielectric mirrors, which exhibit zero space occupancy by exploiting the time dimension, instead of the spatial dimension.

A Machine-Learning-Based Approach to Solve Both Contact Location and Force in Soft Material Tactile Sensors

Abstract: This study addresses a design and calibration methodology based on numerical finite element method (FEM) modeling for the development of a soft tactile sensor able to simultaneously solve the magni...

A High-Precision and Miniature Fiber Bragg Grating-Based Force Sensor for Tissue Palpation During Minimally Invasive Surgery

Abstract: This paper presents a novel Fiber Bragg Grating (FBG)-based palpation force sensor to explore tissue abnormalities during minimally invasive surgery. The proposed sensor design mainly consists of a miniature force-sensitive flexure, one tightly suspended optical fiber embedded with one FBG element and associated connectors and fixations. The flexure design has been prototyped through the configuration synthesis of Sarrus mechanism by using a rigid-body replacement method to achieve an excellent axial linear force–deformation relationship and a large measurement range. The mounted fiber has been configured at the flexure’s central line with its two ends glued, and its tight suspension configuration can achieve improved resolution and sensitivity and avoid the FBG chirping failure compared to the commonly used direct FBG-pasting methods. Finite element method (FEM)-based simulation has been performed to investigate both static and dynamic performance to aid in structural design. Simulation-enabled structural optimization design has also been implemented to further improve the proposed design and the sensor’s sensitivity has been increased. The optimized sensor design has been prototyped and calibrated to demonstrate an excellent linearity with a small linearity error of 0.97% and achieve a high resolution of 2.55 mN within a relatively large measurement range of 0–5 N. Dynamic force stimulation experiments, in vitro palpation implementation on a silicone phantom embedded with simulated tumors and ex vivo indentation experiments on a porcine liver have validated the effectiveness of the presented sensor design.

Scheme of coherent optical chaos communication.

Abstract: We propose and numerically demonstrate a scheme of coherent optical chaos communication using semiconductor lasers for secure transmission of optical quadrature amplitude modulation (QAM) signals. In this scheme, a laser intensity chaos and its delayed duplicate are used to amplitude-quadrature modulate a continuous-wave light to generate a chaotic carrier. High-quality chaotic carrier synchronization between the transmitter and receiver is guaranteed by laser intensity chaos synchronization, avoiding laser phase fluctuation. Decryption is implemented by a 90 deg optical hybrid using the synchronous chaotic carrier as local light. Secure transmission of an optical 40 Gb/s 16QAM signal is demonstrated by using a laser intensity chaos with a bandwidth of 11.7 GHz. The system performances are evaluated by analyzing a bit error ratio with different masking coefficients, signal rates, synchronization coefficients, parameter mismatches, and dispersion compensation. It is believed that this scheme can pave a way for high-speed optical chaos communication.

HER2 biosensing through SPR-envelope tracking in plasmonic optical fiber gratings

Abstract: In the biomedical detection context, plasmonic tilted fiber Bragg gratings (TFBGs) have been demonstrated to be a very accurate and sensitive sensing tool, especially well-adapted for biochemical detection. In this work, we have developed an aptasensor following a triple strategy to improve the overall sensing performances and robustness. Single polarization fiber (SPF) is used as biosensor substrate while the demodulation is based on tracking a peculiar feature of the lower envelope of the cladding mode resonances spectrum. This method is highly sensitive and yields wavelength shifts several tens of times higher than the ones reported so far based on the tracking of individual modes of the spectrum. An amplification of the response is further performed through a sandwich assay by the use of specific antibodies. These improvements have been achieved on a biosensor developed for the detection of the HER2 (Human Epidermal Growth Factor Receptor-2) protein, a relevant breast cancer biomarker. These advanced developments can be very interesting for point-of-care biomedical measurements in a convenient practical way.

Selective detection of cadmium ions using plasmonic optical fiber gratings functionalized with bacteria.

Abstract: Environmental monitoring and potable water control are key applications where optical fiber sensing solutions can outperform other technologies. In this work, we report a highly sensitive plasmonic fiber-optic probe that has been developed to determine the concentration of cadmium ions (Cd2+) in solution. This original sensor was fabricated by immobilizing the Acinetobacter sp. around gold-coated tilted fiber Bragg gratings (TFBGs). To this aim, the immobilization conditions of bacteria on the gold-coated optical fiber surface were first experimentally determined. Then, the coated sensors were tested in vitro. The relative intensity of the sensor response experienced a change of 1.1 dB for a Cd2+ concentration increase from 0.1 to 1000 ppb. According to our test procedure, we estimate the experimental limit of detection to be close to 1 ppb. Cadmium ions strongly bind to the sensing surface, so the sensor exhibits a much higher sensitivity to Cd2+ than to other heavy metal ions such as Pb2+, Zn2+ and CrO42- found in contaminated water, which ensures a good selectivity.

Stabilizing DFB laser injection-locked to an external fiber-optic ring resonator.

Abstract: Self-injection locking to an external fiber cavity is an efficient technique enabling drastic linewidth narrowing and self-stabilization of semiconductor lasers. The main drawback of this technique is its high sensitivity to fluctuations of the configuration parameters and surroundings. In the proposed laser configuration, to the best our knowledge, for the first time the self-injection locking mechanism is used in conjunction with a simple active optoelectronic feedback, ensuring stable mode-hopping free laser operation in a single longitudinal mode. Locking to 4-m length fiber resonator causes a drastic narrowing of the DFB laser linewidth down to 2.8 kHz and a reduction of the laser phase noise by three orders of magnitude. We have explored key features of the laser dynamics with and without active feedback, revealing stability and tunability of the laser linewidth as an additional benefit of the proposed technique.

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

Abstract: 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.

Narrow bandwidth fiber-optic spectral combs for renewable hydrogen detection

Abstract: Hydrogen sensors are of great importance to detect leakage in time because the hydrogen-air mixture is highly flammable. Based on optical fiber-based configurations reported so far, using palladium coating only does not meet stringent performance targets, such as fast response time and limited deactivation caused by poisoning. Here, a palladium-gold alloy-coated optical fiber hydrogen sensor, i.e., highly tilted fiber Bragg grating (TFBG), was proposed by using its narrow bandwidth cladding modes whose effective refractive index (ERI) extends to 1.0 where the gas measurement is possible, which led to faster specific hydrogen measurement response time (a shorter stabilization time during the association and dissociation phases less than 20 s and 30 s, respectively) and improved deactivation resistance (higher than 99% per test cycle). Meanwhile, the temperature cross-sensitivity can be eliminated via referencing the “target” spectral combs to the core mode. We are sure that this promising configuration extends research directions for rapid, repeatable and high deactivation-resistance in hydrogen gas detection.

Simultaneous Measurement of Temperature and Refractive Index Using an Exposed Core Microstructured Optical Fiber

Abstract: We have demonstrated a novel scheme for simultaneous measurement of temperature and refractive index by using an exposed core microstructured optical fiber (ECF). The ECF allows for high sensitivity to refractive index due to the small exposed-core, while being supported by a standard fiber diameter cladding making it robust compared to optical microfibers. The sensor combines a fiber Bragg grating (FBG) inscribed into the core of the ECF and a multimode Mach–Zehnder interferometer (MZI). Both the FBG and MZI are sensitive to refractive index (RI) and temperature through a combination of direct access to the evanescent field via the exposed-core, the thermo-optic effect, and thermal expansion. The FBG and MZI respond differently to changes in temperature and RI, thus allowing for the simultaneous measurement of these parameters. In our experiment, RI sensitivities of 5.85 nm/RIU and 794 nm/RIU, and temperature sensitivities of 8.72 pm/°C and −57.9 pm/°C, were obtained for the FBG and MZI respectively. We demonstrate that a transfer matrix approach can be used to simultaneously measure both parameters, solving the problem of temperature sensitivity of RI sensors due to the high thermo-optic coefficient of aqueous samples.

A fiber Bragg gratings pair embedded in a polyurethane diaphragm: Towards a temperature-insensitive pressure sensor

Abstract: We report the development of a temperature-insensitive pressure sensor based on a pair of fiber Bragg gratings (FBGs) embedded in a polyurethane diaphragm The pressure is transversely applied, causing a bending on the diaphragm In such condition, the FBGs are positioned in opposite directions considering the diaphragm bending’s neutral line as a reference Thus, when the pressure is applied on the diaphragm, the wavelength shift occurs in opposite directions, ie, one FBG has a blue shift and the other, red shift The wavelength shift difference between both FBGs is analyzed, leading to a system with higher sensitivity when compared with the individual responses of each FBG In addition, if the temperature sensitivities of each FBG are compensated, there is no difference in the wavelength shift (considering the difference between both FBGs) when the system is subjected only to temperature variations However, if the system suffers simultaneous variation of temperature and pressure, there is a variation in the pressure sensitivity due to changes in the elastic modulus of the diaphragm caused by the temperature variations For this reason, a compensation approach is proposed using the wavelength shift of each FBG as well as their difference The sensor was tested for temperature, pressure and moisture absorption, where the maximum wavelength shift for the moisture absorption was 4 pm For temperature and pressure responses, the sensor presented high sensitivity and linearity for all analyzed cases, leading to a pressure resolution of 175 Pa for constant temperature conditions In pressure cycles under different temperatures, the compensation technique showed the feasibility of applying the proposed sensor in practical applications, where temperature variations as high as 30 °C were tested The sensor presented a temperature cross-sensitivity of 033 Pa/°C

Pose Measurement of Flexible Medical Instruments Using Fiber Bragg Gratings in Multi-Core Fiber

Abstract: Accurate navigation of flexible medical instruments like catheters require the knowledge of its pose, that is its position and orientation. In this paper multi-core fibers inscribed with fiber Bragg gratings (FBG) are utilized as sensors to measure the pose of a multi-segment catheter. A reconstruction technique that provides the pose of such a fiber is presented. First, the measurement from the Bragg gratings are converted to strain then the curvature is deduced based on those strain calculations. Next, the curvature and the Bishop frame equations are used to reconstruct the fiber. This technique is validated through experiments where the mean error in position and orientation is observed to be less than 4.69 mm and 6.48 degrees, respectively. The main contributions of the paper are the use of Bishop frames in the reconstruction and the experimental validation of the acquired pose.

A High-Resolution Triaxial Catheter Tip Force Sensor With Miniature Flexure and Suspended Optical Fibers

Abstract: This article reports a miniature, high-resolution fiber Bragg grating (FBG)-based triaxial force sensor to detect the catheter tip–tissue interaction forces. This sensor counts on a delicate three-dimensional-printed flexure comprising a cylinder with an inner elliptical cavity for detecting lateral forces and a hybrid elastomer to enhance axial elasticity for improving z -directional force sensitivity. Four suspended optical fibers inscribed with FBG each are deployed inside the flexure. Such configurations are designed to maximize the decoupling among three force components, achieve temperature compensation, and raise the sensor's robustness under biofluid-filled environments. The sensor characterization results indicate a high resolution of 0.52 and 0.64 mN for both lateral forces within –0.8 to 0.8 N and 0.63 mN for axial direction force within 0–0.8 N. Validation with dynamic loadings along different azimuth angles shows that the sensor can provide a high-accuracy measurement of three force components with an rms error of less than 3.00%. Temperature-induced errors for force detection are considerably alleviated, showing less than 6.5% in the range of 25 °C–50 °C. Ex vivo experiments on a swine heart further validate the performances of the designed sensor.

Distributed multicore fiber sensors

Abstract: Multicore fiber (MCF) which contains more than one core in a single fiber cladding has attracted ever increasing attention for application in optical sensing systems owing to its unique capability of independent light transmission in multiple spatial channels. Different from the situation in standard single mode fiber (SMF), the fiber bending gives rise to tangential strain in off-center cores, and this unique feature has been employed for directional bending and shape sensing, where strain measurement is achieved by using either fiber Bragg gratings (FBGs), optical frequency-domain reflectometry (OFDR) or Brillouin distributed sensing technique. On the other hand, the parallel spatial cores enable space-division multiplexed (SDM) system configuration that allows for the multiplexing of multiple distributed sensing techniques. As a result, multi-parameter sensing or performance enhanced sensing can be achieved by using MCF. In this paper, we review the research progress in MCF based distributed fiber sensors. Brief introductions of MCF and the multiplexing/de-multiplexing methods are presented. The bending sensitivity of off-center cores is analyzed. Curvature and shape sensing, as well as various SDM distributed sensing using MCF are summarized, and the working principles of diverse MCF sensors are discussed. Finally, we present the challenges and prospects of MCF for distributed sensing applications.

Closed-Loop Temperature Control Based on Fiber Bragg Grating Sensors for Laser Ablation of Hepatic Tissue.

Abstract: Laser ablation (LA) of cancer is a minimally invasive technique based on targeted heat release. Controlling tissue temperature during LA is crucial to achieve the desired therapeutic effect in the organs while preserving the healthy tissue around. Here, we report the design and implementation of a real-time monitoring system performing closed-loop temperature control, based on fiber Bragg grating (FBG) spatial measurements. Highly dense FBG arrays (1.19 mm length, 0.01 mm edge-to-edge distance) were inscribed in polyimide-coated fibers using the femtosecond point-by-point writing technology to obtain the spatial resolution needed for accurate reconstruction of high-gradient temperature profiles during LA. The zone control strategy was implemented such that the temperature in the laser-irradiated area was maintained at specific set values (43 and 55 °C), in correspondence to specific radii (2 and 6 mm) of the targeted zone. The developed control system was assessed in terms of measured temperature maps during an ex vivo liver LA. Results suggest that the temperature-feedback system provides several advantages, including controlling the margins of the ablated zone and keeping the maximum temperature below the critical values. Our strategy and resulting analysis go beyond the state-of-the-art LA regulation techniques, encouraging further investigation in the identification of the optimal control-loop.

An enhanced WDM optical communication system using a cascaded fiber Bragg grating

Abstract: In this paper, a cascaded fiber Bragg grating (FBG) system is proposed to reduce the dispersion in the optical signal in single mode optical fibers. This consequently enhances the system performance, which is evaluated by the bit error rate (BER) and quality factor (Q-factor). The proposed model consists of four uniform cascaded FBGs connected at the transmitter to get narrow linewidth, Δλ, of the optical signal, which is a major cause of the delay. The Optisystem7 is used to simulate the proposed model in a WDM system with and without the model for distance 200 km. The system parameters are investigated showing an enhanced performance with 12%, including eye diagram, Q-factor and BER. A 10−6–10−10 BER is achieved with a quality factor in the range 7–14, including the effects of fiber length, input power and FBG length.