Fiber Optic Transducer Research Articles

High-Performance Fiber Optic High-Frequency Cantilever Acoustical Transducer Based on PET Film

High-Performance Fiber Optic High-Frequency Cantilever Acoustical Transducer Based on PET Film

Multi-point fiber optic laser-ultrasonic transducer based on long-period fiber grating

For ultrasonic non-destructive testing, the development of miniaturized, embeddable, and distributed ultrasonic transducers has always been a hot research topic. In light of this, a novel fiber optic laser-ultrasonic transducer, employing the long-period fiber grating (LPFG), was introduced in this study to facilitate the implementation of embedded and distributed applications. LPFG couples the light transmitted in the optical fiber into the photoacoustic conversion material. After the energy conversion of optic-heat-acoustic, ultrasonic waves can be excited. The finite element models of the mode coupling and photoacoustic conversion of LPFG were established. The transmission spectrum and optical power of LPFG were measured by experiments. The results show that by adjusting the structural parameters of LPFG to make it appear as different transmission depths, the quantitative control of the optical power distribution of the core and cladding can be realized. Two LPFGs, each with distinct coupling coefficients, were fused together and anchored onto aluminum plates to create an ultrasonic transducer with dual micro-ultrasonic sources. An ultrasonic excitation experiment was carried out, and the results revealed that both two LPFGs could excite ultrasonic waves with a peak-to-peak value of about 500 mV and a center frequency of about 3 MHz. The study validates the proposed fiber-optic ultrasonic transducer's steady performance and its potential for multi-point applications.

Development of an ultrasonic wave measurement device based on Fiber Bragg Gratings in optical fibers: application to Guided Wave Structural Health Monitoring

Optical fiber transducers such as Fiber Bragg Gratings (FBG) are promising solutions for guided waves Structural Health Monitoring (SHM) due to their low intrusivity and their ability to cope with harsh environments (extreme temperatures, radiations, explosive atmospheres…). We present here a solution enabling measurements under varying environmental and operational conditions, which is mandatory for many applications in SHM, the low complexity of the solution ensuring good integration capacities. The effect of the length of the FBG was also studied to enable the optimization of the system sensitivity.

Temperature-insensitive label-free SARS-CoV-2 spike protein detection based on complementary refractive index and temperature dependence of multi-mode interference and grating resonance

We demonstrated temperature-insensitive, label-free detection of SARS-CoV-2 spike protein (SSP) by harnessing the complementary refractive index and temperature dependence of multi-mode interference (MMI) created by a no-core fiber (NCF) and phase-matched resonance generated by a long-period fiber grating (LPFG). To combine MMI and grating resonance, primarily sensitive to the surrounding medium refractive index (SMRI) and ambient temperature, respectively, a fiber-optic transducer was fabricated by splicing an NCF segment with an LPFG inscribed on double-clad fiber. The transducer was functionalized with human ACE2 receptors to selectively capture SSP. The functionalized sensor head exhibited high SSP selectivity, with overall average wavelength displacements of ∼253.33 and ∼160.00 pm in PBS and saliva, respectively, for SSP with concentrations ranging from 1 to 104 ng/mL. These spectral shifts are associated with localized SMRI modulations on the sensor surface induced by specific binding between SSP and ACE2. We also examined the cross-reactivity of the sensor head for MERS-CoV spike protein to confirm its SSP specificity. Moreover, we proved the capability of temperature-independent SSP detection and ambient temperature measurement by scrutinizing the temperature effect on the sensor performance. Our functionalized fiber transducer showed great promise as a temperature-insensitive and portable platform for rapid SSP detection.

Fiber Optic Photoacoustic-Based Steering Imaging Transducer

This letter presents a novel fiber optic imaging transducer for solving ultrasound steering problems for photoacoustic imaging (PAI). The design of the transducer is explored and verified by photoacoustic (PA) effect and Fabry-Perot (FP) principle. A directional ultrasound beam that is based on PA effect is excited by coating gold nanocomposites with polydimethylsiloxane (PDMS) at the distal end of an optical fiber with a certain degree of offset. A microlens with a concave surface is attached to the surface to focus on the length of ultrasound waves. A pulse echo signal is collected by an FP fiber optic sensor. Ultrasound field distribution is captured in order to confirm that the ultrasound beam is directional and focused as a result of the microlens. B mode imaging tests on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ex vivo</i> swine back rib muscle-fat slices report the transducer to own a higher depth of penetration. Ultrasound imaging is formed by combining the scanned pulse echo signal without the need for an image reconstruction algorithm. The results demonstrate a promising foundation for the prototype of the fiber optic ultrasound imaging transducer in terms of challenging environments and in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vivo</i> .

Experimental investigation on performance monitoring of the combined optical fiber transducer in landslide

An innovative combined optical fiber transducer (COFT) based on the optical fiber bending loss characteristic has been developed for landslide monitoring. To better understand the working principle and improve the monitoring performance of the transducer, the capability of the COFT for exploring subsurface properties of slopes (sliding direction, magnitude, and rate of slope movement) and the deformation compatibility between the COFT and surrounding geo-materials were explained semi-empirically and semi-theoretically, which was also verified by the laboratory shear experiments of the COFTs constructed with two kinds of host materials (expanded polystyrene and polyvinyl chloride) and three kinds ratios of cement mortars (sand to cement 1:4, 1:5, and 1:6) and the related numerical simulation. In the following, model monitoring tests of an artificial slope and field monitoring application of the proposed COFTs in a field slope were carried out and the progressive slope movements were effectively determined, which validated the performance of the proposed COFT in landslide monitoring.

Technology and Application Progress of Fiber-Optic Ultrasound Transducer

Technology and Application Progress of Fiber-Optic Ultrasound Transducer

Bite Force Transducers and Measurement Devices.

In dental research, bite force has become an important curative effect evaluation index for tooth restoration, periodontal treatment, and orthodontic treatment. Bite force is an important parameter to evaluate the efficacy of the masticatory system. Physicians obtain the therapeutic basis for occlusal adjustment by measuring the bite force and the dynamic changes in occlusal contact at different stages of treatment and objectively evaluate the therapeutic effect. At present, many devices are used to record the bite force. Most of these devices use force transducers to detect bite force, such as strain gauge transducers, piezoresistive transducers, piezoelectric transducers, optical fiber transducers, and pressure-sensitive films. This article summarizes the various equipment used to record bite force, related materials and the characteristics of this equipment. It provides a reference for physicians to make choices during the clinical process and at the same time provides a basis for the development of new occlusal force measurement materials.

Mechanically robust amino acid crystals as fiber-optic transducers and wide bandpass filters for optical communication in the near-infrared

Organic crystals are emerging as mechanically compliant, light-weight and chemically versatile alternatives to the commonly used silica and polymer waveguides. However, the previously reported organic crystals were shown to be able to transmit visible light, whereas actual implementation in telecommunication devices requires transparency in the near-infrared spectral range. Here we demonstrate that single crystals of the amino acid L-threonine could be used as optical waveguides and filters with high mechanical and thermal robustness for transduction of signals in the telecommunications range. On their (00bar 1) face, crystals of this material have an extraordinarily high Young’s modulus (40.95 ± 1.03 GPa) and hardness (1.98 ± 0.11 GPa) for an organic crystal. First-principles density functional theory calculations, used in conjunction with analysis of the energy frameworks to correlate the structure with the anisotropy in the Young’s modulus, showed that the high stiffness arises as a consequence of the strong charge-assisted hydrogen bonds between the zwitterions. The crystals have low optical loss in the O, E, S and C bands of the spectrum (1250−1600 nm), while they effectively block infrared light below 1200 nm. This property favors these and possibly other related organic crystals as all-organic fiber-optic waveguides and filters for transduction of information.

Optical Fiber Sensors by Direct Laser Processing: A Review.

The consolidation of laser micro/nano processing technologies has led to a continuous increase in the complexity of optical fiber sensors. This new avenue offers novel possibilities for advanced sensing in a wide set of application sectors and, especially in the industrial and medical fields. In this review, the most important transducing structures carried out by laser processing in optical fiber are shown. The work covers different types of fiber Bragg gratings with an emphasis in the direct-write technique and their most interesting inscription configurations. Along with gratings, cladding waveguide structures in optical fibers have reached notable importance in the development of new optical fiber transducers. That is why a detailed study is made of the different laser inscription configurations that can be adopted, as well as their current applications. Microcavities manufactured in optical fibers can be used as both optical transducer and hybrid structure to reach advanced soft-matter optical sensing approaches based on optofluidic concepts. These in-fiber cavities manufactured by femtosecond laser irradiation followed by chemical etching are promising tools for biophotonic devices. Finally, the enhanced Rayleigh backscattering fibers by femtosecond laser dots inscription are also discussed, as a consequence of the new sensing possibilities they enable.

Optical ultrasound (OpUS): a novel concept for intravascular imaging

Abstract Aims To evaluate whether Optical Ultrasound (OpUS), a novel method for performing ultrasound imaging, could provide compelling, real-time visualizations of coronary vasculature. Methods and results With current commercial intravascular ultrasound (IVUS) devices, piezoelectric transducers are used to electrically generate and receive Ultrasound (US). With this paradigm, there are several challenges that limit further improvement in image resolution. Firstly, with increasing miniaturization of these piezoelectric transducers it can be difficult to achieve adequate sensitivity and bandwidth for high resolution imaging. Secondly, the complexities associated with fabricating and electrically connectorising broadband piezocomposite transducers can result in high manufacturing costs. Lastly, with increasing interest in identifying the molecular composition of atherosclerotic plaque, it has been challenging to achieve high resolution and high imaging depths, whilst also allowing for hybrid imaging with photoacoustics (PA) or near-infrared spectroscopy (NIRS). With OpUS, US is generated at the surface of a fibre optic transducer via the photoacoustic effect. Here, pulsed or modulated light from a laser source is transmitted along the fibre, absorbed in a coating on the fibre surface and converted to thermal energy. The subsequent heat rise leads to a corresponding pressure rise within the coating which propagates as ultrasound. This process is facilitated through the use of custom, engineered nanocomposite materials comprising an optical absorber with an elastomeric host. US reflections from tissue are received with optical interferometry in a method similar to optical coherence tomography (OCT) signal interrogation. For this study we included these elements into a probe and imaged ex-vivo coronary artery tissue. A novel, optically-selective nanocomposite coating enabled concurrent OpUS and PA imaging for molecular contrast using the same imaging probe. Using OpUS we demonstrated high resolution imaging (&amp;lt;40 microns axial), large imaging depths (&amp;gt;2 cm) of coronary tissue and performed a comparison with histology. Numerous features of atherosclerotic plaque were identifiable, including a lipid pool, a calcified nodule, and the different layers comprising the vessel wall. The fiber-optic transducer generated ultra-high pressures and bandwidths: 21.5 MPa and 39.8 MHz respectively. Hybrid imaging using OpUS and PA was also demonstrated, highlighting regions with high lipid content. Conclusion This new platform for intravascular imaging offers high resolution equivalent to 60 Mhz high-definition IVUS whilst maintaining deep tissue penetration. Hybrid imaging with PA can be used for directly visualizing lipid plaque. OpUS transducers are highly flexible, with small diameters (&amp;lt;400 microns) and have low fabrication costs, making them well suited for incorporation into interventional devices. Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Wellcome Trust/EPSRC, National Institute for Health Research Biomedical Research Centre - University College London

Optically Generated Ultrasound for Intracoronary Imaging.

Conventional intravascular ultrasound (IVUS) devices use piezoelectric transducers to electrically generate and receive US. With this paradigm, there are numerous challenges that restrict improvements in image quality. First, with miniaturization of the transducers to reduce device size, it can be challenging to achieve the sensitivities and bandwidths required for large tissue penetration depths and high spatial resolution. Second, complexities associated with manufacturing miniaturized electronic transducers can have significant cost implications. Third, with increasing interest in molecular characterization of tissue in-vivo, it has been challenging to incorporate optical elements for multimodality imaging with photoacoustics (PA) or near-infrared spectroscopy (NIRS) whilst maintaining the lateral dimensions suitable for intracoronary imaging. Optical Ultrasound (OpUS) is a new paradigm for intracoronary imaging. US is generated at the surface of a fiber optic transducer via the photoacoustic effect. Pulsed or modulated light is absorbed in an engineered coating on the fiber surface and converted to thermal energy. The subsequent temperature rise leads to a pressure rise within the coating, which results in a propagating ultrasound wave. US reflections from imaged structures are received with optical interferometry. With OpUS, high bandwidths (31.5 MHz) and pressures (21.5 MPa) have enabled imaging with axial resolutions better than 50 μm and at depths >20 mm. These values challenge those of conventional 40 MHz IVUS technology and show great potential for future clinical application. Recently developed nanocomposite coating materials, that are highly transmissive at light wavelengths used for PA and NIRS light, can facilitate multimodality imaging, thereby enabling molecular characterization.

Optical Fiber Transducer for Monitoring Single-Phase and Two-Phase Flows in Pipes

Fluid flow monitoring is essential in many industrial processes. However, some flow measurement methods may not be feasible in a few applications such as the ones in potentially explosive atmospheres or under presence of intense electromagnetic fields. In this study, we present the construction and evaluation of an optical fiber transducer, which is suitable for flow monitoring in industrial environments pipes. Besides single-phase flow, which has been already monitored by similar techniques in the past, we also present in this paper the measurement of two-phase gas-liquid flows. Working principle is based on the measurement of the force induced by the streaming fluid into a cantilever whose deformation is indirectly and optically monitored by means of fiber Bragg gratings. Static and dynamic tests were performed for transducer calibration and validation. In static calibration, sensor sensitivity to force corresponded to 2.34 nm/N. The transducer was successfully applied to measure single-phase flow rate in the range of 0 $\text{m}^{{3}}$ /h to 6.68 $\text{m}^{{3}}$ /h, presenting maximal uncertainty of 0.3 $\text{m}^{{3}}$ /h. Finally, the transducer was applied in two-phase gas-liquid flow, being able to correctly identify gaseous and liquid phases since the cantilever is exposed to different forces during the passage of the gas and liquid. In this way, the developed transducer may be well applied to two-phase flow monitoring.

Field-Programmable Gate Array-Based Hardware Design of Optical Fiber Transducer Integrated Platform

This study focuses on the hardware architecture of a Raman scattering distributed optical fiber transducer platform, the principles of Raman scattering are analyzed, and the output 2 analog electrical signals are converted to digital signals at a 16-bit sampling rate by an Analog-to-Digital Converter (ADC). The system is implemented based on the FPGA. The integrated circuit is responsible for controlling the data acquisition process. The differential amplifier circuit, FPGA peripheral circuit, and CPU subsystem circuit, which takes ARM as the core, are separately designed. The composition of software includes a DDR2 (Double Data Rate 2) driver and central control logic. In this study, the optical fiber transducer platform has been tested. The CPU DDR2 is read/written by the test program respectively. According to the results, the program passes the read/write test. The NAND FLASH is tested. The results show that this program returns all operations successfully. The timing tests of the DDR2 interface and data latching are conducted. The results show that the read/write operations ensure that the clock and data curves are aligned. Therefore, the optical fiber transducer integrated platform designed in this study is effective.

Comprehensive theoretical study of optical, thermophysical and acoustic properties of surface nanostructures with metallic nanoparticles for fiber-optic photoacoustic ultrasound transducers

Comprehensive theoretical study of optical, thermophysical and acoustic properties of surface nanostructures with metallic nanoparticles for fiber-optic photoacoustic ultrasound transducers

Low cost, high sensitivity detection of waterborne Al3+ cations and F− anions via the fluorescence response of a morin derivative dye

Morin dye is known as a cheap and readily available selective ‘off → on’ fluorescent sensitiser when immobilised in a phase transfer membrane for the detection of Al3+ ions. Here, a morin derivative, NaMSA, which readily dissolves in water with good long-term stability is used in conjunction with a fibre optic transducer with lock-in detection to detect Al3+ in drinking water below the potability limit. The combination of a water soluble dye and the fibre optic transducer require neither membrane preparation nor a fluorescence spectrometer yet still display a high figure-of- merit. The known ability to recover morin-based Al3+ cation sensors selectively by exposure to fluoride (F−) anions is further developed enabling a complementary sensing of either fluoride anions, or aluminium cations, using the same dye with a sub-micromolar limit-of-detection for both ions. The sensor performance parameters compare favourably to prior reports on both aqueous aluminium and fluoride ion sensing.

Cerebellar-cortical function and connectivity during sensorimotor behavior in aging FMR1 gene premutation carriers

IntroductionPremutation carriers of the FMR1 gene are at risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative disease characterized by motor, cognitive, and psychiatric decline as well as cerebellar and cerebral white matter pathology. Several studies have documented preclinical sensorimotor issues in aging premutation carriers, but the extent to which sensorimotor brain systems are affected and may represent early indicators of atypical neurodegeneration has not been determined. Materials and methodsEighteen healthy controls and 16 FMR1 premutation carriers (including five with possible, probable, or definite FXTAS) group-matched on age, sex, and handedness completed a visually guided precision gripping task with their right hand during fMRI. During the test, they used a modified pinch grip to press at 60% of their maximum force against a custom fiber-optic transducer. Participants viewed a horizontal white force bar that moved upward with increased force and downward with decreased force and a static target bar that was red during rest and turned green to cue the participant to begin pressing at the beginning of each trial. Participants were instructed to press so that the white force bar stayed as steady as possible at the level of the green target bar. Trials were 2-sec in duration and alternated with 2-sec rest periods. Five 24-sec blocks consisting of six trials were presented. Participants’ reaction time, the accuracy of their force relative to the target force, and the variability of their force accuracy across trials were examined. BOLD signal change and task-based functional connectivity (FC) were examined during force vs. rest. ResultsRelative to healthy controls, premutation carriers showed increased trial-to-trial variability of force output, though this was specific to younger premutation carriers in our sample. Relative to healthy controls, premutation carriers also showed reduced extrastriate activation during force relative to rest. FC between ipsilateral cerebellar Crus I and extrastriate cortex was reduced in premutation carriers compared to controls. Reduced Crus I-extrastriate FC was related to increased force accuracy variability in premutation carriers. Increased reaction time was associated with more severe clinically rated neurological abnormalities. ConclusionsFindings of reduced activation in extrastriate cortex and reduced Crus I-extrastriate FC implicate deficient visual feedback processing and reduced cerebellar modulation of corrective motor commands. Our results are consistent with documented cerebellar pathology and visual-spatial processing in FXTAS and pre-symptomatic premutation carriers, and suggest FC alterations of cerebellar-cortical networks during sensorimotor behavior may represent a “prodromal” feature associated with FXTAS degeneration.

Synthesis, Structural and Spectral Properties of Surface Noble Metal Nanostructures for Fiber-Optic Photoacoustic Generation

The method for synthesis of noble metal nanoparticles monolayers on the surface of optical fiber edge is proposed. Structural and optical spectral properties of such nanostructures are studied from the viewpoint of photoacoustic fiber-optic generation. In this paper, we examined experimentally surface nanostructures previously simulated for photoacoustic fiber-optic transducers.

Validation of an ultrasound transducer's generation and receiving function on one single-mode fiber

This paper presents the design, fabrication and testing of a single-mode fiber optic ultrasound transducer. This transducer can work as an ultrasound generator and a receiver, based on principles of photoacoustic (PA) effect and Fabry–Pérot (FP) interference. PA effect is a process in which ultrasound waves are generated from optical energy by a PA material, and an FP structure is used for ultrasound receiving. The transducer was manufactured by coating a material called gold nanocomposite directly onto a single-mode optical fiber tip. The gold nanocomposite acted as the PA material and formed the FP structure as well. The transducer had the same size as the single-mode fiber, whose diameter was only 125 μm. It demonstrated its ability to generate ultrasound signals with a bandwidth of 5.6 MHz at an efficiency of 3.2 × 10−5 and function as an ultrasound receiver with a sensitivity of 2.81 mV/MPa. The generator and receiver built together can currently only work separately. This new transducer has substantial potential to work in restricted space and harsh environments for non-destructive testing.

Ultrasound beam steering using a fiber optic ultrasound phased array.

In this Letter, a novel fiber optic ultrasound phased-array technology is proposed to solve the ultrasound beam steering problems for fiber optic ultrasound biomedical imaging. The ultrasound beam steering feasibility is explored and verified by our unique time-delay approach. A theoretical analysis is performed to predict the beam steering angle. Experiments have been performed to verify that the ultrasound beam is steered by using our approach. Four fiber optic ultrasound generators were fabricated and used to build the phased-array emitter. The successful accomplishment of this project established a foundation of the prototype of the fiber optic ultrasound imaging transducer.