Types Of Fiber Optic Sensors Research Articles

Fiber-Optic Sensor Spectrum Noise Reduction Based on a Generative Adversarial Network

In the field of fiber-optic sensing, effectively reducing the noise of sensing spectra and achieving a high signal-to-noise ratio (SNR) has consistently been a focal point of research. This study proposes a deep-learning-based denoising method for fiber-optic sensors, which involves pre-processing the sensor spectrum into a 2D image and training with a cycle-consistent generative adversarial network (Cycle-GAN) model. The pre-trained algorithm demonstrates the ability to effectively denoise various spectrum types and noise profiles. This study evaluates the denoising performance of simulated spectra obtained from four different types of fiber-optic sensors: fiber Fabry–Perot interferometer (FPI), regular fiber Bragg grating (FBG), chirped FBG, and FBG pair. Compared to traditional denoising algorithms such as wavelet transform (WT) and empirical mode decomposition (EMD), the proposed method achieves an SNR improvement of up to 13.71 dB, an RMSE that is up to three times smaller, and a minimum correlation coefficient (R2) of no less than 99.70% with the original high-SNR signals. Additionally, the proposed algorithm was tested for multimode noise reduction, demonstrating an excellent linearity in temperature response with a R2 of 99.95% for its linear fitting and 99.74% for the temperature response obtained from single-mode fiber sensors. The proposed denoising approach effectively reduces the impact of various noises from the sensing system, enhancing the practicality of fiber-optic sensing, especially for specialized fiber applications in research and industrial domains.

Experimental study on practical application of optical fiber sensor (OFS) for high-temperature system

This study explores the application of Raman scattering-based optical fiber sensors (OFSs) in extreme environments, specifically focusing on a loop heater vessel with temperatures ranging from 200 °C to 680 °C. This condition generally covers the advanced reactor designs, such as Sodium-cooled Fast Reactor and High Temperature Reactor. Various optical fiber combinations were employed for temperature measurements, taking into consideration the operating temperature of the target equipment. Two types of OFSs, gold-coated and polyimide-coated, were utilized. Protective tubes made of stainless steel (STS) and carbon were introduced to ensure reliable temperature data collection in high-temperature settings. Results indicate that the STS tube with a gold-coated OFS exhibited the highest consistency and agreement with thermocouple measurements, making it suitable for extreme environments. The study emphasizes the applicability of this system in high-temperature environments, such as liquid metal reactors, high-temperature thermal energy storage system, and hydrogen production system, for environmental monitoring.

Innovative optical pH sensors for the aquaculture sector: Comprehensive characterization of a cost-effective solution

Optical fiber sensors show potential for monitoring multiple parameters essential to the growth and health of fish, particularly the pH value of the aquaculture medium. Two types of optical fiber sensors, using tapered silica single mode fibers with a Bragg grating inscribed and D-shaped plastic optical fibers (home-made and reused) were produced. A pH-sensitive layer made of polyaniline (PANI) was deposited on the optical fibers’ surface. The sensors demonstrated reproducibility and repeatability with a sensitivity of −0.22 ± 0.02 dB/pH, −472 ± 9 Counts/pH, and −(26 ± 2) × 102 Counts/pH for tapers, D-shape home-made, and reused, respectively, but only for increasing pH. Stabilization time tests indicated that a minimum of 60 s is required for a stable response, with no significant cross-sensitivities regarding temperature and ionic strength.

Graphene Oxide Doped Alginate Coated Optical Fiber Sensor for the Detection of Perfluorooctanoic Acid in Water

A novel and easy to fabricate graphene doped alginate thin film (Alg /GO) capable of binding with perfluorooctanoic acid (PFOA) and working on the principle of a Fabry-Perot interferometry (FPI) type optical fiber sensor is presented here. Utilizing a simple dip coating technique, the Alg/GO coating was deposited on the freshly cleaved fiber end-face followed by cross-linking in calcium chloride. The experimental results from two independent data analysis techniques, including Fourier-transform infrared (FTIR) spectroscopy and analytical adsorption tests were used to confirm that the developed graphene doped alginates can adsorb PFOA. It was also found that GO doped alginate coating adsorbs twice as much PFOA compared to alginate alone. Similarly, experimental results of the developed FPI sensor demonstrate the sensitivity to PFOA in aqueous solutions with a limit of detection (LOD) of 0.4 ppb and a non-linear correlation between 0 to 2 ppb with increasing concentration of PFOA in water. The response time at this concentration was estimated to be 17 s, considering a thin film coating thickness of approximately 30 μm as determined via imaging with the aid of differential interference contrast (DIC) microscopy. The relatively high sensitivity and ease of formation of the coating offers the potential for future development of portable optical sensors for emerging environmental contaminants.

Long Distance Military Fiber-Optic Polarization Sensor Improved by an Optical Amplifier

The ever-increasing demands for the use of fiber-optic sensors powered by long optical fibers is forcing developers to solve problems associated with powering these remote sensors. Due to their non-electric character, these sensors are suitable for many uses, including military applications. The Army of the Czech Republic is very interested in this type of optical fiber sensor as it fulfils the significant prerequisites for use in military areas. However, the army’s requirements are challenging because they require long supply cables in which there is significant attenuation of optical power. At the same time, there is a need for high sensitivity. The subject of our research team’s work was to use amplifiers to power these sensors. The army already uses this type of sensor for short distances as it cannot ignite a gas mixture with an explosive concentration and thus meet the strict requirements of the explosion-poof standard. The novelty of our research lies in the discovered measurement technique that allows the sensors to be powered remotely and in the saving of optical fibers by utilizing duplex communication with a circulator. Furthermore, the research presents an innovative approach to the optimization of the entire sensor by using a bidirectional, sensory, polarization-maintaining optical fiber. The proposed sensor was first verified in laboratory conditions at the Optoelectronics Laboratory of the University of Defense in Brno, and further tests were carried out in the military training areas of Boletice and Březina in the Czech Republic, which is a member of North Atlantic Treaty Organization.

Analysis of Optical Communications, Fiber Optics, Sensors and Laser Applications

The fields of optical communications, fiber optics, and sensors and laser applications have undergone significant evolution, revolutionizing the way we transmit and receive data and having a profound impact on various industries. With ongoing advancements and research, these fields hold immense potential for future developments. In-depth information on optical communications, fiber optics, and sensors may be found in this study. The constraints and limits of optical communications as well as the qualities of optical fibers and the many kinds of optical fibers utilized in optical communications are discussed. Additionally, it also covers the use of fiber optics in sensing applications, different types of fiber-optic sensors, and recent developments and future trends in the field. The article provides a comprehensive overview of the current state of the field, highlighting the significance of technology and its impact on various industries. The article also aims to give readers a better understanding of the current state of the field and its potential for future developments.

Marine Structural Health Monitoring with Optical Fiber Sensors: A Review.

Real-time monitoring of large marine structures' health, including drilling platforms, submarine pipelines, dams, and ship hulls, is greatly needed. Among the various kinds of monitoring methods, optical fiber sensors (OFS) have gained a lot of concerns and showed several distinct advantages, such as small size, high flexibility and durability, anti-electromagnetic interference, and high transmission rate. In this paper, three types of OFS used for marine structural health monitoring (SHM), including point sensing, quasi-distributed sensing, and distributed sensing, are reviewed. Emphases are given to the applicability of each type of the sensors by analyzing the operating principles and characteristics of the OFSs. The merits and demerits of different sensing schemes are discussed, as well as the challenges and future developments in OFSs for the marine SHM field.

Simultaneous Measurement of Strain and Temperature Distributions Using Optical Fibers with Different GeO2 and B2O3 Doping.

Compensating for the effects of temperature is a crucial issue in structural health monitoring when using optical fiber sensors. This study focused on the change in sensitivity due to differences in GeO2 and B2O3 doping and then verified the accuracy when measuring the strain and temperature distributions simultaneously. Four types of optical fiber sensors were utilized to measure the strain and temperature in four-point bending tests, and the best combination of the sensors resulted in strain and temperature errors of 28.4 μϵ and 1.52 °C, respectively. Based on the results obtained from the four-point bending tests, we discussed the error factors via an error propagation analysis. The results of the error propagation analysis agreed well with the experimental results, thus indicating the effectiveness of the analysis as a method for verifying accuracy and error factors.

Strain registration in the gradient zone by two types of fiber-optic sensors

Reliable measurement of strain in various sections of the monitored structure is an important problem for creating Structural Health Monitoring systems. Fiber-optic sensors have great potential to solve this problem. This paper presents the results of experiments on strain measurements in zones of homogeneous and gradient strain distribution using point fiber-optic sensors based on Bragg gratings and distributed fiber-optic sensors based on Rayleigh backscattering. Two types of fiber-optic sensors have demonstrated the ability to measure an inhomogeneous strain field and a satisfactory correspondence of the measurement results.

High-performance temperature and pressure dual-parameter sensor based on a polymer-coated tapered optical fiber

Based on the polymer encapsulation method, a compact structure and high-sensitivity temperature and pressure dual parametric sensor was developed in this paper by wrapping an optical microfiber coupler (OMC) in polydimethylsiloxane (PDMS). Benefiting from the stable chemical properties and good optical field control ability of PDMS, the sensor showed good stability and repeatability. The dependence of the sensor sensitivity on wavelength, temperature, and pressure was experimentally investigated. The results showed that the temperature and pressure sensitivity could reach -2.283 nm/°C and 3.301 nm/Mpa in the C-band range. To overcome the cross-sensitivity of sensor temperature and pressure, a sensitivity matrix was established to realize dual-parameter simultaneous demodulation. In addition, the pressure repeatability of the sensor was tested. Based on this, the sensitivity matrix was further calibrated to reduce the error and improve the accuracy of demodulation. Finally, we also designed a protective shell for the sensor to meet the requirements of practical marine applications. Compared with other existing types of optical fiber sensors, this sensor has the advantages of simple fabrication, high sensitivity, and environmental adaptability, and has great potential for application in the field of marine environmental monitoring.

Vibration-based monitoring of an FRP footbridge with embedded fiber-Bragg gratings: Influence of temperature vs. damage

An attractive feature of FRP structures is that Fiber-Optic Sensors (FOS) can be naturally embedded during the production process and provide important structural information immediately after construction. Thus, FOS became very useful also for Vibration-Based Monitoring (VBM) applications. In VBM, damage can be identified by detecting damage-related changes in the modal characteristics of a structure, such as natural frequencies and strain mode shapes. However, natural frequencies can exhibit a low sensitivity to certain types of damage, especially when compared to their sensitivity to temperature. Strain mode shapes though have been proved to be more sensitive to local damage and less to temperature than natural frequencies. In this work, an FRP footbridge is subjected to periodic annual VBM. The dynamic strains of the bridge are monitored with embedded Fiber-optic Bragg Gratings (FBG), a type of FOS that allows determining natural frequencies and strain mode shapes accurately from low-amplitude strain data. Vibration modes are identified from the dynamic strains and the influence of temperature and heavy loading is investigated. The identified modes are used for calibrating a finite element model. Possible damage scenarios on FRP structures are simulated and their influence on modal characteristics is investigated and compared to this of temperature.

Measurement of strain and temperature by fiber-optic sensors embedded into samples manufactured by additive technology

The paper demonstrates the possibility of using embedded point and distributed fiber-optic sensors to register data on the mechanical state of structures made by fused deposition modeling from thermoplastic materials. The performance of two types of fiber-optic sensors was demonstrated at the stage of sample fabrication. Uniform strength beam was taken as a sample. Temperature and strain were continuously recorded using the embedded fiber-optic sensors during the sample fabrication. Based on the readings of point and distributed fiber-optic sensors, graphs and surfaces of strain and temperature distributions along the length of the sample over time are presented. These parameters allow further evaluation of the inhomogeneity of strain and temperature distribution along the sample. Comparison of the experimental data obtained from two types of fiber-optic sensors during the sample fabrication was carried out.

Sensor integration and data explotation of Structural Health Monitoring Network integrated on a Unmananned Aerial Vehicle (UAV)

Unmanned Aerial Vehicles (UAVs) are flying robots that require little or no human control while flying. The number of UAV has growth exponentially due to rise in applications such as video taking, surveillance and delivering cargo to customers. Despite the promise of the technology, UAV are not very reliable currently, either civil or military. They lack of sensing mechanisms to detect issues in operation, such impacts, hard landings and overload, together with the difficulties to detect structural problems during the UAV operation could compromise not only the safety of the UAV, also all along the entire flying area. This paper presents the design, development implementation, and validation of a Structural Health Monitoring (SHM) system applied to the rear fuselage of the UAV developed by INTA for R&D activities (MILANO). The rear fuselage, a 2.5 meters carbon/epoxy structure with frames and stringers, was instrumented with fiber optic sensors and PZT. Two different types of fiber optic sensors were considered: Fiber Bragg Gratings and distributed fiber sensing based on Rayleigh backscatter. The objective of the fiber optic sensor network is to detect the changes induced on the strain field due to damage appearance. This information will be employed to train a neural network which provides the self-diagnosis of the structural integrity. Additionally, the PZT network will be used as active system for structure interrogation through elastic waves.

Enhanced fiber mounting and etching technique for optimized optical power transmission at critical cladding thickness for fiber-sensing application

Optical fibers offer various applications to cater to industrial needs, from power and data transmission to environmental sensing. Different sensing mechanisms of optical fibers depend on modifications made to the fiber itself primarily in the cladding and core sections. Different types of optical fiber sensors may require thinning of the cladding to allow propagated light to interact closer to the environmental stimuli. Chemical etching is commonly used for the de-cladding of a fiber, and there are many ways to execute this method. A conventional method of chemical etching is typically used for cladding removal. This paper reports and discusses the effectiveness of enhanced techniques for improvement towards conventional chemical etching methods with the assistance of a makeshift fiber holder. The fiber holder allows the fiber to be oriented well, allowing for smoother etching and thus conserving its mechanical structure. Thickness reduction is seen to be more consistent when the enhanced technique is employed, and the fiber takes a longer time (∼45 min) to break. This allows etching of the cladding close to the core, which is more manageable for the user if very thin cladding is required. A fiber etched without any holder tends to break earlier (∼35 min) than expected with a rather wide error margin. The lower coefficient of determination, R 2 values (95%) of the thickness reduction from conventional etching shows irregular thickness along the fibers. Optical power also fluctuates between 30–35 dBm for the conventional method, while the mounted fiber technique maintains stable optical power at 50 dBm during etching. Therefore, it is concluded that proper fiber horizontal fiber orientation during etching has a significant effect on the fiber strength due to the smooth cladding removal around the corecore while minimizing any permanent power loss to or the occurrence of fluctuations in the fiber. This smooth and efficient etching technique allows the production of enhanced fiber sensors with minimal structural or power defects.

Load estimation and vibration monitoring of scale model wind turbine blades through optical fiber sensors

Experimental activities on wind turbine models allow to speed up their design as well as the development of robust and effective control algorithms. Intending to have large information on load distribution on the blades, this work presents an experimental setup of a model wind turbine blade instrumented with two different types of optical fiber sensors (FOS). The first one is a traditional chain of Fiber Bragg Grating sensors, able to measure a large number of strain values; the second is based on Optical Backscatter Reflectometry (OBR), able to provide a continuous strain measurement. The experimental setup is calibrated to estimate load distribution along the blade and the two technologies are compared. The results of the experimental campaign suggest that optical fiber sensors could represent an interesting solution for real-time continuous load monitoring purposes.

Review of fiber optic sensors for corrosion monitoring in reinforced concrete

Monitoring corrosion in reinforced concrete is critical to assess the health condition of structures at an early stage and enable effective and efficient asset management. Various novel fiber optic sensors have been developed and demonstrated many advantages in monitoring corrosion in reinforced concrete under different conditions. However, currently, there is a gap between sensor technology innovation and engineering practices, and the gap hinders further development and wide applications of fiber optic sensors. This paper reviews representative types of fiber optic sensors for monitoring corrosion in reinforced concrete. The reviewed types of sensors include grating sensors, interferometer sensors, distributed sensors, and reflectometer sensors. For each type of sensors, the reviewed contents include the sensing principle and key features of applications, such as sensor design and installation, sensitivity, resolution, and sensor life. Emphasis is placed on discussing the functions and performance of the sensors in different corrosion stages. Based on the review, technical challenges and future research needs are identified and discussed. This review is expected to advance sensor development and promote effective applications of fiber optic sensors for intelligent structures and asset management.

Comparison of three types of fiber optic sensors for temperature monitoring in a groundwater flow simulator

Different fiber optic sensors have been used for groundwater temperature monitoring and the question is which one to choose for a particular study. In the field conditions it is sometimes difficult to determine how much error is introduced by the sensor placement technique, packaging or cross-sensitivity between temperature and strain. These factors were studied in a laboratory groundwater simulator during a heat tracing experiment. The performance of three fiber optic technologies was evaluated – distributed temperature sensing, fiber Bragg gratings and continuous fiber Bragg gratings. All sensors had comparable accuracy of around 0.2 °C and resolution smaller than 0.1 °C. Therefore, factors which need to be considered when choosing a sensor for groundwater temperature monitoring are spatial resolution, sampling frequency and possibility to measure absolute/relative temperature. The experiment also showed that strain effects can be introduced even when fibers have a loose tube packaging.

Fiber Optic Sensors: A Review for Glucose Measurement.

Diabetes mellitus is a chronic metabolic disorder, being globally one of the most deadly diseases. This disease requires continually monitoring of the body’s glucose levels. There are different types of sensors for measuring glucose, most of them invasive to the patient. Fiber optic sensors have been proven to have advantages compared to conventional sensors and they have great potential for various applications, especially in the biomedical area. Compared to other sensors, they are smaller, easy to handle, mostly non-invasive, thus leading to a lower risk of infection, high precision, well correlated and inexpensive. The objective of this review article is to compare different types of fiber optic sensors made with different experimental techniques applied to biomedicine, especially for glucose sensing. Observations are made on the way of elaboration, as well as the advantages and disadvantages that each one could have in real applications.

Convergence deformation monitoring of a shield tunnel based on flexible long-gauge FBG sensors

For subway safety, it is important to monitor the convergence deformation of shield tunnels in the long term. However, traditional monitoring methods are constrained by high cost and technical difficulties. Herein, improvements achieved through use of a new type of optical fiber (OF) sensor are reported. The new type of optical fiber sensor, namely, the flexible long-gauge Fiber Bragg Grating (FBG) sensor, is proposed with descriptions of design, preparation and strain sensing performance. Then, a method of assessing convergence deformation is proposed based on distributed long-gauge strain measurements. Finally, the proposed method is validated with measurements made on two full size specimens of shield segments. It is also concluded that the seam change shows a strong influence on convergence deformation. From static experiments, convergence deformation can be accurately evaluated to satisfy the demands of tunnel management. Considering the additional advantages of distributed sensing, such as sensing distance, stability and durability, the proposed method exhibits broad application prospects.

A fluorometric metal-organic framework oxygen sensor: from sensitive powder to portable optical fiber device

Abstract Nowadays, the development of high-sensitivity oxygen probes and portable detection devices are urgent required. Lanthanide metal-organic frameworks (MOFs), combining the advantages of lanthanide luminescent features and the inherent porosity of MOFs, show great potential for highly sensitive O2 sensing. At the same time, optical fiber sensors have proven to be a simple and effective detection platform for portable and actual monitoring. In this work, we designed an O2-sensitive porous lanthanide MOF by elaborately selecting organic ligand with the suitable high triplet-state level. The luminescent intensity of as-synthesized EuNDC (1,4-H2NDC = 1,4-naphthalenedicarboxylic acid) can be effectively quenched by O2, giving rise to the most outstanding detection performance than other reported lanthanide MOFs with high sensitivity (93.5% quenched at 1 bar O2, I0/I100 = 15.4, KSV = 13.3 bar-1, LOD = 0.21 mbar), good reversibility, and short response/recovery times (10/70 s). After that, we proposed and developed a reflection type optical fiber sensor by integrating EuNDC and silica fiber in PDMS film for remote, in-field and real-time O2 monitoring.