Optical Fibers and Sensors for Medical Diagnostics, Treatment and Environmental Applications XXIV

We report a graphene oxide integrated optical biosensor for the detection of breast cancer cell media. The principle of the optical biosensor is based on alerting the optical signal as a change of local refractive index caused by different analyte concentration. The graphene oxide nanosheets coated long period grating (GO-LPG) served as optical transducer where the GO overlay acted as a bridging interface between optical sensor and external cancer cell medium. The proposed biosensor was implemented to detect the breast cancer cell media with ultrahigh sensitivity, opening the path as a bio-nano-photonic platform for biosensing and early diagnosis.

Hair-thin optical fiber endoscopes have opened new paradigms for advanced imaging applications, such as optical coherence tomography, which a large depth-of-field is desirable to trade off lateral and axial resolutions. This requirement can be achieved using needle-like Bessel beams, generated by micro-lenses bonded onto fiber tips. In this paper, we compare Fresnel zone plate and axicon mask on fiber tips shaping light into Gaussian foci and Bessel beams, and demonstrate that the axicon-fiber device is capable of imaging a resolution target with large depth-of-field. We also show that our fabrication method is capable of fabricating fiber-imaging devices with multi-layer lens stacks.

We propose a side-view OCT imaging method that rotates the probe beam and reflects it in all directions using a conical mirror. A small conical mirror was made with a mirror-coated plastic optical fiber processed into a cone. The resulting probe was inserted into the interior of a cylindrical sample to easily acquire circumferential OCT images without mechanical rotation. The proposed probe can be utilized as an alternative to solve the problems of conventional side-view imaging probes. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (grand no. NRF-2017R1A2B2009732).

Calcium phosphate glass based single-mode and multi-mode bioresorbable optical fibers were in-house manufactured. Ex-vivo studies were then conducted to test the suitability of these fibers for time gated diffuse optics spectroscopy, photodynamic therapy and diffuse correlation spectroscopy applications which can be respectively employed for the diagnosis, treatment, and monitoring of malignant tissues. The results demonstrated the potential of calcium phosphate glass-based fiber optic devices towards the realization of an implantable multi-functional class of devices with functionalities ranging from cancer detection to monitoring of the healing process all integrated into a single bioresorbable platform. Acknowledgement: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 860185

Hypoxic tumours are known to demonstrate significant resistance to cancer radiotherapy treatments requiring real-time monitoring of oxygen concentration within the tumour. A novel optical fibre sensor based on Fabry Perot interferometric technique is proposed in this paper for real-time oxygen measurement through the refractive index changes corresponding to the changes in oxygenation levels within a hypoxic tumour. The sensor proposed demonstrates the potential to open the possibility of adapting the radiation dose delivered during the course of the radiotherapy treatment as per the tumour hypoxia levels.

Healthcare monitoring systems using mid-infrared and deep ultraviolet spectroscopy.

Water electrolysis in Proton Exchange Membrane Water Electrolysis (PEMWE) cells is important for sustainable energy conversion. The efficiency and longevity of these cells depend on operating conditions such as the temperature of the membrane. We employ a fiber-based sensor using lanthanide-doped nanoparticles as nanothermometers to measure the temperature at the cell’s membrane for different operational conditions. In the future, this sensor can be used to optimize the cell’s operational parameters and is also applicable in strong electromagnetic fields, for example in battery technology or magnetic resonance tomography.

The paper discusses all-fiber applicators for the percutaneous laser ablation of tumors, which integrate very dense fiber Bragg grating arrays to add quasi-distributed sensing capabilities. First an assessment of the temperature map distribution reconstruction from the measurements is presented and the impact of some nonidealities is studied; then the developed probes are used to analyze different laser operating conditions, comparing the measurements in ex-vivo porcine livers with modeling expectations.

Addressing the pressing need for rapid and sensitive infectious disease diagnostics, we introduce DIgitAl plasMONic nanobubble Detection (DIAMOND), an innovative strategy harnessing plasmonic nanobubbles generated through laser-induced nanoparticles. Using gold nanoparticles in an optofluidic system, DIAMOND enables compartment-free digital counting and homogeneous immunoassays, demonstrating respiratory syncytial virus detection at single RNA copy per microliter. This breakthrough technology offers single-nanoparticle detection, direct virus sensing at room temperature, and simplified liquid handling, establishing itself as a versatile platform for expedited and highly sensitive diagnostics, with the added benefit of achieving detection within just 10 minutes. Concurrently, our research advances plasmonic nanobubble generation by anchoring sub-10 nm AuNPs onto thiol-rich Qβ virus-like particles, significantly enhancing photocavitation and reducing laser fluency. In a significant step forward, we are expanding the horizons of DIAMOND, now enabling single protein detection at attomolar concentrations, representing a remarkable advancement in our capabilities.

Rapid and sensitive assessment of biomedical compounds as well as environmental markers have become a critical pursuit of our community. Implementation of a combination of complementary and orthogonal sensing schemes, such as, fiber-coupled Raman and THz spectroscopy and imaging systems could revolutionize the sensing field even outside the laboratory by providing fast, reliable, non-contact, non-invasive acquisitions in the domains of environmental sensing and biomedical diagnostics.

In this paper, we discuss the development of the optical fibre multiparameter sensing system for application in chronic wound healing measurements. The system consists of temperature, humidity, ammonia, and CO2 optical fibre sensors operating in reflection mode. The tip of the fibre is coated with the sensitive layer to provide specificity towards the specific measurands. The sensors’ performance is presented using Bland-Altman plots.

We report a fiber-optic sensor that can be deployed through a standard 250-µm injection needle (25 gauge) for minimally invasive measurements of deep-tissue biomechanical properties in vivo. We have demonstrated the sensor’s ability to provide distinct readouts of muscle stiffness when the hind limb of a rat is relaxed and stretched. To ensure minimal tissue damage and distortion, we have integrated optical proximity sensing within the same fiber for real-time, precise control of the sensor position. To facilitate clinical translation, we have designed the sensor to be disposable and autoclavable and have developed a strategy for mass production.

A new fiber has been developed at Polymicro which has been optimized to significantly improve long term optical transmission stability under high power conditions, such as with Xenon and laser-driven plasma sources. This fiber has been demonstrated to remain stable in the spectral region of 190nm to 1800nm. The fiber is thermostable up to 150°C. In addition, the fiber has demonstrated excellent resistance to X-ray and Gamma radiation.

Dopamine, a vital neurotransmitter in the human body, plays a crucial role in various physiological functions and is closely associated with neurological disorders such as Parkinson's disease. Timely and accurate detection of dopamine levels is essential for effective disease management and personalized healthcare. In this study, we propose an innovative optical fiber-based biosensor utilizing the Localized Surface Plasmon Resonance (LSPR) effect for highly sensitive and selective dopamine detection. The biosensor probe is fabricated using a SMS (Single mode fiber-Multimode fiber-Single mode fiber) optical fiber structure, which is chemically modified to enhance the LSPR effect. Gold nanoparticles are employed to amplify the plasmonic response, enabling improved sensing performance. Experimental analysis is performed using dopamine samples, and the results are obtained using a spectrometer. The developed LSPR biosensor demonstrates great potential for precise and efficient dopamine detection, paving the way for advanced personalized healthcare and improved management of neurological disorders.

The Fabry-Perot interferometer (FPI) is a key component in a fiber-optic sensor that operates based on wave interference and light resonance. It utilizes optical interference to generate distinctive interference patterns. In this study, a blood Fabry-Perot interferometer integrated into a single-mode fiber is used to detect blood clot formation by monitoring changes in the interference pattern. This sensor design offers high sensitivity and rapid response, enabling real-time monitoring of physiological parameters and potential applications in various fields, particularly in medical diagnostics and monitoring. Further exploration in this area holds great potential for enhancing optical sensors, advancing biophysical and medical research.

Tapered optical fiber sensor (TOFS) devices are attractive as biosensors due to their high sensitivity and accurate measurement capabilities reaching 10pg/ml, and real-time operation. The tapered region allows the evanescent electromagnetic (EM) field to extend outside the fiber to enable the detection of minute changes in the refractive index in close proximity to the tapered region. The sensing is achieved using appropriate functionalized tapered fiber surfaces. In this work, a second generation (2G) automated compact TOFS system developed in our lab is tested, and repeatable and stable signals are obtained proving that this device potentially can serve as a portable bio/chemical sensor in the future. Preliminary simulations of optical propagation through the tapered fiber leading to the detected signal are presented.

We propose a highly sensitive extrinsic Fabry-Perot interferometer fiber-optic microphone for detecting low concentrations of trace gases based on Photoacoustic spectroscopy. A theoretical model is set up to predict the mechanical behavior of the sensor and extended with a mathematical framework for the detection of gas concentration from the generated acoustic modes in a gas cell. The gas molecules are excited with a laser diode of 50 mw power and the detection limit of 41.53 ppb Nitric Oxide (NO) is calculated for a minimum detectable pressure of 2.1μpa/√Hz for the sensor. We have further confirmed the analytical results with experiments.

The paper presents an all-optical system for the detection of bacterial contaminations in flowing water that combines the readings from a multi-functional fiber Surface Plasmon Resonance (SPR) sensor with fluorescence measurements. The application to cases of water contaminated with E. Coli is discussed.

We demonstrate a portable optical sensor that utilizes a functionalized tapered fiber and phase shift-cavity ringdown spectroscopy to detect LAM (a Tuberculosis (TB) biomarker) in aqueous solutions. To specifically target LAM in a solution, we develop a functionalization process that involves a silanization step followed by anchoring an aldehyde-bearing monolayer onto the fiber's surface. The surface aldehyde groups facilitate the covalent attachment of CS-35 LAM antibodies. Our experimental results show a minimum detection limit of 2 pg/ml and a sensitivity of 2.74 °/(mg/l). Our proposed sensor will lead to rapid, specialist-free, non-invasive TB diagnostics platforms.

We report on fluorescence enhancement using a suspended core photonic crystal fiber (PCF) as an optofluidic platform. By employing metallic nanoparticles and an organic spacer, we achieved a thirty-fold signal enhancement of Cy5 dye at picomolar concentrations. The combination of fluorescence enhancement and PCF offers robustness, ease of use, and high sensitivity. This comprehensive study explores fluorescence enhancement using PCF, highlighting the significant enhancement achieved through metallic nanoparticles and organic spacers associated by the long length of light-analyte interactions offered by the PCF. These findings might contribute to the development of highly sensitive optical fiber-platforms for biomedical applications.

We present new connection concepts for optical fibers, which cannot be connected using conventional connectors or splicing. An aluminosilicate glass substrate with femtosecond laser written waveguides (LWW) is used as interposer between the 2 optical fibers. We are testing different methods for realizing optical connections with the help of this interposer. One possible method relies on evanescent waveguide coupling between the optical (sensing) fiber and a LWW. In addition, we will demonstrate results of fs-laser written Bragg gratings, integrated in the glass with the goal to add monitoring capabilities to the interposer. We will present the different steps and in between results to develop the interposer.

A compact fiber-optic probe for combinational vibrational spectroscopy was developed and evaluated. The probe is capable of simultaneous acquisition of mid-infrared ATR and Raman spectra from the same spot in the region 3100-2600 cm-1 which contains predominantly the responses of C-H stretching vibrations of hydrocarbon residues that has been widely employed in organic, analytic, biological, and polymer chemistry.

The infection of coronavirus is caused upon the binding between the human angiotensin-converting enzyme 2 receptor (ACE2) and (SARS-Cov-2) spike protein (S). To mimic the spike-ACE2 biorecognition event, the functionalized gold chip with self-assembled layers (SAMs) composed of 3-mercaptopropionic acid and NHS/EDC was prepared to immobilize the ACE2 bioreceptor as a surface plasmon resonance (SPR) platform to capture the spike protein. The target antibody concentration can be correlated with the SPR peak shift of Au nanofilm caused by the refractive index change due to the chemical bond created on the Au chip and also to the antigen–antibody binding.

Edible oil adulteration poses a significant threat to public health and erodes consumer trust in the food industry. This study presents an innovative approach to detect edible oil adulteration by leveraging the capabilities of Fibre Bragg Grating (FBG) sensors, known for their speed and accuracy. The FBG sensors were employed to monitor the refractive index (RI) of edible oils, enabling the identification of adulterants introduced during the adulteration process, such as lower-quality oils and non-edible contaminants. Rigorous experiments were conducted to assess the FBG sensor's efficacy in detecting adulteration. The remarkable sensitivity and specificity of the FBG sensor were demonstrated through its ability to detect and measure even minute changes in RI induced by the presence of adulterants. The findings suggest that a system based on FBG sensors holds immense potential as a fast and non-destructive method for ensuring the authenticity of edible oils and safeguarding consumer health.

Infrared imaging from space provides critical information about Earth’s surface and atmosphere for weather prediction, study of the world’s ecosystems, detection and monitoring of natural disasters such as volcanoes and wildfires. In the recent decade, JPL IR group has been developing high performance imagers that are based on the novel infrared detector technology. In my presentation I will discuss our advances in mid- and long- wavelength infrared FPAs and their use in remote sensing instruments.

Owing to the recent technological advances in mid-infrared (3-15 µm; MIR) laser technology, especially cascade laser spectroscopy (CSL) has evolved into a state-of-the-art tool for the selective and sensitive quantification of trace analytes in liquid, solid, and gaseous state in a wide variety of sensing scenarios. High output power, narrow linewidths, single-mode operation, low power consumption, broad tunability and compact dimensions are just some of the most outstanding features of cascade lasers. The unique combination with mid-infrared fiberoptic facilitates the development of innovative MIR catheter technologies for analyzing cartilage damage in-vivo during arthroscopic surgery.

To address the concern of personal privacy invasion by cameras, this paper proposes a real-time human recognition system using fiber-optic distributed acoustic sensors (DAS) to achieve human identification and monitoring while prioritizing privacy protection. The system employs an optical fiber engraved with multiple Rayleigh-enhanced points placed on the ground to detect vibrations caused by individuals walking. A phase-sensitive OTDR is utilized to analyze the vibration patterns at various positions along the optical fiber. For recognizing individuals, a four-layer CNN network is developed, utilizing the detected vibration patterns induced by human walking. The CNN is trained using a dataset of five hundred data collections from four test subjects walking on the ground. To ensure real-time performance, the system is enhanced using FPGA acceleration techniques. This involves widening the data interface, increasing parallel processing capabilities, and optimizing the calculation pipeline. In testing, the system achieved an impressive 86% accuracy in pedestrian recognition, confirming its effectiveness in real-time scenarios.

There is a multibillion-dollar market for gas monitoring and the demand for solutions continues to grow. Managing methane leaks is critical for energy operations, monitoring nitrogen species in agriculture has ramifications for crop health, and toxic gases in multiple industries can create hazardous working conditions. Many systems rely on optical techniques, light sources and photonic detectors working together to produce measurements. When considering the wavelengths to utilize, operating in the mid-infrared region presents advantages such as higher sensitivity, longer lifetimes, and more consistent measurements. Components have been known to be expensive and difficult to integrate but recent developments present new opportunities. This presentation will cover the basic principles of photonic gas measurements, the state of current and future mid-infrared components, and the science behind the benefits of mid-infrared for gas analysis.

The mid-IR wavelength range, and the fundamental vibrational absorption fingerprint region it encompasses, can be utilised for a variety of environmental and medical monitoring applications requiring the detection of specific covalently bonded molecules, for example, in atmosphere or in a patient’s breath. Mid-IR transmitting chalcogenide fibres, based on the elements: sulfur, selenium, and tellurium, have a characteristically high optical non-linearity and thus can be tailored to also generate mid-IR supercontinuum light that covers this fingerprint region. The process of designing, fabricating, and characterising chalcogenide glass fibres via differential scanning calorimetry, microscopy, ellipsometry, and optical fibre loss measurements is detailed.

Monitoring remote drinking water purification facilities presents a global challenge that impacts human and environmental well-being. The lead time between sampling and analysis of the water output from these facilities hinders the identification of, and a fast response to, system failures. Here, we employ plasmonic metasurfaces as ‘nano-tastebud’ sensors for real-time, inline testing of drinking water. Our sensor demonstrates > 95% accuracy when distinguishing between treated and untreated water. Once fully developed, this system could be integrated into water treatment facilities to warn of imminent system failures.

In this study, we developed a label-free plasmonic biosensor chip that can detect PFOA in real-time. Perfluorooctanoic acid (PFOA) is widely used in several industries. It is a toxic chemical found in the environment that accumulates in food. A microfluidic chamber was used to increase the precision and stability of the LSPR signals. We demonstrated PFOA sensing at concentrations of 100 µM and 500 µM. The preliminary results demonstrate the good real-time sensing capability of the fiber-optic microfluidic LSPR setup. Acknowledgement: This work has received funding from VILLUM FONDEN (Villum Investigator project Table-Top Synchrotrons, No. 00037822) and Green Development, and Demonstration Program under the Danish Ministry for Food, Agriculture and Fisheries (GeoZense, 34009-20-1769).

We report on the development of mid-infrared spectroscopy-based sensors for inline water and wastewater analysis. Mid-infrared spectroscopy is a powerful tool for chemical identification and quantification. To overcome the limitations of the technique imposed by rapid extinction of the infrared signal in water, we have developed pre-concentration techniques that achieve at least two orders of magnitude enhancement of measurement sensitivity, along with enhanced selectivity, for select analytes. Applications include monitoring of nutrients and metabolites in bioreactor systems for wastewater treatment and industrial processes (e.g. biofuel production), in-line process control in chemical manufacturing, and rapid on-site screening of contaminants in environmental samples.

Myron Block of the eponymous Block Engineering, along with his colleagues, pioneered the development of the rapid-scan FTIR which uses a HeNe laser to precisely track the position of the moving mirror in a scanning Michelson interferometer. This fundamental technology from the late 1960s, which enabled the development of the modern FTIR, was spun out into the Block subsidiary Digilab, Inc., who both made instruments and licensed the technology. Block Engineering continued to innovate with compact and portable FTIR systems for chemical detection and analysis. More recently, Block has focused on development of external-cavity quantum cascade lasers (EC-QCLs). The high spectral and spatial brightness of these widely tunable mid-infrared lasers make the EC-QCL much more suitable standoff chemical detection. This retrospective explores the history of light sources in the mid-IR up to the present day, and extends current technology to provide a view towards evolving future systems.

Surface Enhanced Raman Spectroscopy (SERS) is widely recognized for its efficacy in the detection of trace contaminants. However, its potential for quantitative analysis is still being investigated. This study demonstrates the suitability of ink-jet printed SERS (P-SERS) substrates for quantitative SERS analysis of trace levels of pesticides. Data was collected using a Standard Operating Procedure (SOP) and analyzed with a chemometrics model. The obtained R2 value, nearing 0.99, and a standard error (SE) of ~0.7 μM, indicate a strong correlation and precision in the tests conducted using P-SERS, covering pesticide concentrations ranging from 0.0 to 20.0 μM.

This paper explores how a fluorescent dye can be immobilized in a polymer film at the distal end of an optical fibre to serve as a fibre optical chemical sensor for organic solvents in water. The sensing principle is based on a shift in the fluorescence peak of the dye.

Long-Period Fiber Gratings (LPFGs) have found extensive applications in refractive index sensing for chemical and biomedical purposes. This paper explores a novel method of fabricating dynamic LPFGs based on the principle of acousto-optic effect. The propagation of ultrasonic waves within the fiber optic induces periodic elastic strain of the fiber, leading to corresponding changes in the fiber's refractive index over time and space. By modulating the characteristics of the ultrasound, various types of LPFGs can be generated. The feasibility of this method is verified through experiments, and two special gratings, namely dynamic phase-shifted long-period fiber grating and dynamic chirped long-period fiber grating, are fabricated based on the variations in ultrasonic characteristics. This development presents a new technique for addressing fiber optic sensing requirements and opens avenues for the future applications such as the detection of immunoglobulin, bacteria, DNA and other targets.

Here we present our latest fiber-optic techniques in spectral range from UV to mid-infrared for research and industrial applications. Depending on the chemical process or materials to be analyzed, fiber probes can be based on 4 different fiber types selected for the required spectral range and used for Transmission, Reflection, ATR-absorption, Raman & Fluorescence spectroscopies. Advanced fiber optic combi probes are capable to utilize two and more spectroscopic methods at the same time assembled in the same probe shaft - such as Mid-FTIR+Fluorescence, Raman+Near IR, Raman+Mid-FTIR, Raman+mid-FTIR-Near IR and others. It improves selectivity and precision of the analysis for media content in process control.

Bioproduction is becoming increasingly important for the pharmaceutical industry. Real-time contaminant monitoring during each drug purification stage would be a great asset. The presentation will focus on a custom silicon photonics platform based on silicon nitride biofunctionalized Mach Zehnder Interferometers. We will show how these label-free and multiplexed biosensors can detect contaminants below the µg/ml within a few tens of seconds and address the issue of the parasitic signal due to the presence of the product of interest at much higher concentrations. Finally, a performance benchmark will encompass component and system-level optimizations such as sensitivity, drift, compactness and microfluidic packaging.

Multimaterial, multifunctional fiber sensors are becoming better candidates for sensing different signals for a variety of applications due to their improved functionalities. We present a sub-THz fiber antenna to detect local deformations of fiber and environmental perturbations in the fiber’s proximity with high sensitivity and spatial resolution. The electromagnetic pulse sent by time-domain reflectometry (TDR) resolves the location of the change on the fiber with a sense of both deformations through the fiber in antisymmetric mode and proximity in the symmetric mode. This multifunctionality broadens the application area of the fiber from biomedical engineering to cyber-physical interfacing.

Optical fiber shape sensing has diverse applications in medical and industrial fields. However, commercially available fiber shape sensors are costly and complex. The development of eccentric fiber Bragg grating (eFBG) sensors provides a cost-effective alternative with unique capabilities. Existing eFBG shape sensing methods calculate curvature using Bragg signal intensity variations. Yet, uncontrolled bending and polarization-dependent losses cause spectral distortions affecting eFBG intensity ratios. To overcome this, we developed a data-driven deep-learning technique for accurate shape prediction. Our approach significantly improves shape prediction, achieving millimeter-level accuracy for curvatures of 3 cm to 70 cm in a 30 cm eFBG sensor. This promising research advances low-cost and accurate fiber sensors, impacting medical and industrial sectors requiring precise and cost-effective shape sensing.

In this study, simulated by using Finite-Difference Time-Domain method, and applied to spin-coating titanium dioxide (TiO2) solution onto the indium tin oxide (ITO) conductive glass films, and gold nanoparticles (AuNPs) are modified on the TiO2 glass films by using self-assembly method. The sensing element is immersed in five different concentrations of glucose solution, including 0 mg/dl, 50 mg/dl, 100 mg/dl, 150 mg/dl and 200 mg/dl. The results show that the resonance wavelength λSPR was shifted by changing the polarization state of the incident light for the purpose of copper ion (Cu2+) concentration sensing.

The development of rapid and precise methods for detecting metal ions has emerged as a critical concern. In this study, we present a novel and highly miniaturized glass capillary system designed for the specific, rapid, and cost-effective detection of heavy metal ions, focusing on chromium (Cr3+) as a representative example. Applied capillaries were made of fused silica (tailored and drawn in-house), and their used pieces accommodated volumes as low as 2.9 µL. The measurement setup consisted of the laser source and optical detector collecting spectra in the wavelength range of 200-900 nm. The specificity of the detection in the system was provided by the engineered green fluorescent protein (eGFP, developed in-house), which undergoes conformational changes upon interaction between its engineered metal-binding loop - and specific metal ion. Consequently, the fluorescence emission of eGFP is either emitted or enhanced. The obtained results clearly demonstrate distinct changes in fluorescence intensity corresponding to varying concentrations (50 pM to 50 µM) of metal ions. Detection of 500 pM was feasible even with the mere presence of ng of the receptor protein - eGFP.

The discharge of hazardous chemicals into the water resources has not only polluted those resources but also caused an existential threat to marine life and humans. Therefore, detection and alerting of such toxic and hazardous chemicals in the water is of utmost importance. In this work, we report a novel knot-type Panda fiber-based hydrazine sensor for the detection of one such hazardous chemical hydrazine. The sensing part of multi-wall carbon nanotubes (MWCNTs) and gold nanoparticles (Au NPs) coated knot-type Panda fiber was carefully shaped into a loop knot for the effective interaction of evanescent waves with the surrounding environment. As a result, the developed sensor showed impressive sensitivity of 0.0674 nm/ppm with a high level of linearity at 0.97. The compact size of the sensor, its ability to mitigate electromagnetic interference, and its excellent repeatability characteristics are the other distinguished advantages offered by the developed sensor.

Power-over-fiber (PoF) is a novel power transmission technology that uses optical fibers, instead of the traditional copper wires, to deliver electrical power to feed remote sensors or electrical devices. This paper experimentally demonstrates a PoF system using off-the-shelf components to feed microelectronics for low-power applications. Experimental results show that simultaneous data signal and power signal can be successfully transmitted using an optical communication link. In particular, the System Energy Efficiency (SSE) is studied, and the effects of signal data-rate and link length on the SSE are investigated.

The existing optical fiber network can be leveraged to serve as a wide distributed network of sensors, especially to detect mechanical stress as the optical signal phase and polarization are significantly influenced by external disturbances. The purpose is to examine the changes in the state of polarization caused by birefringence induced by seismic events and explores how to differentiate these changes from those induced by other events. This will enable us to detect earthquakes, initiate emergency plans upon P-wave arrivals, and implement measures such as early warning alerts, emergency response mechanisms, and immediate cutoffs of gas and electricity utilities to prevent secondary disasters such as fires.

The modern telecommunications infrastructure relies heavily on widely deployed optical fibre networks which serve as its cornerstone. Strains in the fibres are caused by mechanical forces from various sources of ambient vibrations such as human activities and seismic movements. This results in phase shifts in the light that travels through the fibres. Consequently, these phase shifts can be measured across the entire fibre, providing information about the initial vibration events, which makes them an ideal candidate for distributed seismic sensing.

A cross-sensitivity free double-parameter distributed fiber sensing system that utilizes a specialty fiber with double-Brillouin peaks with almost similar levels of gain amplitudes is proposed. By incorporating this fiber into a conventional Brillouin optical time domain analyzer setup, simultaneous and accurate sensing of strain and temperature was achieved with high accuracies of strain ( ±13 με) and temperature (±0.5 °C). The proposed specialty fiber exhibits minimal Brillouin frequency shift (BFS) errors (<0.18 MHz), enhancing measurement accuracy. These specialty fibers offer potential benefits in applications like long-distance natural gas pipeline monitoring where simultaneous strain and temperature monitoring is crucial.

Various fiber-optic sensing applications, particularly for strain and temperature monitoring, widely employ stimulated Brillouin scattering (SBS). However, SBS-based sensors using standard fibers like single-mode fibers (SMFs), suffer from strain-temperature cross-sensitivity, which limits their accuracy and reliability. To overcome this challenge, specialty fibers have been explored, offering significant advantages over SMFs. Here, we numerically investigate the design tradeoffs of ring-core fibers (RCFs), for discriminative strain and temperature sensing. We identify essential design guidelines to achieve high sensitivity, accuracy, and selectivity in strain and temperature measurements. Our investigations offer valuable insights into the optimization of RCFs for advanced and versatile sensing systems.

Cellulose, as a fully renewable, biodegradable, and biocompatible material, creates new possibilities to human health monitoring with optical fiber sensors. Here we demonstrate a face mask that contains regenerated cellulose optical fiber with a 2.2 dB/cm attenuation constant for respiratory rate monitoring. The cellulose fiber inside the face mask rapidly moistens and dries between each breath, which causes a periodic change in optical power transmitted through the fiber. A face mask does not prevent fast drying of the fiber. Cellulose optical fiber length was 3-5 cm with a loop-type sensor structure. Measured respiratory rates varied between 20-40 breaths per minute.

For monitoring temperature and strain in harsh hydrogen environments, fiber Bragg gratings are inscribed in carbon-coated glass fibers using point-by-point manufacturing technique by applying femtosecond laser pulses with a center wavelength of 400 nm or 800 nm. The signal attenuation of the FBGs were examined to monitor the degration of the fiber in pure hydrogen atmosphere.

Wideband wavelength swept lasers (WSLs) are widely used as light sources for dynamic fiber optic sensors. In this study, we implemented an ultra-wideband wavelength-swept laser (WSL) that achieved a 10 dB bandwidth over 430 nm using a single polygonal scanning mirror-based wavelength tunable filter. The wavelength scanning range with a 1.8kHz scanning frequency is 1136.0~1567.2nm. Comparing the WSL output signal in the temporal and spectral domains resulted in an error of 0.7 nm in the mid-crossing region of the two gain media. To confirm WSL performance, the transmission band was measured by changing the electric field applied to the cholesteric liquid crystal cell, and it was confirmed that the transmitted beam according to the applied electric field matched each other in the spectral and temporal domains.

Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that can detect trace quantities of analyte. However, fabricating cost–effective and homogeneous SERS substrates for diverse applications remains a significant challenge. Herein, a simple bottom-up technique is reported for developing a unique SERS substrate by exploiting the plasmonic coupling of low-cost aluminium foil (ALF) and 3-dimensional (3D) gold nanoparticle aggregates induced by cucurbit[5]uril (CB[5]) .

In this study, the feasibility of a volatile organic compounds (VOC) gas sensor was confirmed through a porous cholesteric liquid crystal film (CLCF) coated on the cross-section of an optical fiber ferrule. The device was fabricated by injecting the CLCF mixture between two ferrules and then UV cured. After separating the two ferrules, porous CLCF was prepared by immersing the CLCF-coated ferrule in acetone. To measure the change in the reflection spectrum of the device for each VOC gas, a broadband wavelength swept laser with a 10dB bandwidth of ~430nm was used. In conclusion, it was found that the reflection band was continuously red-shifted for acetone gas and THF gas.

Photoplethysmography (PPG) is a well-established technique to extract valuable physiological information such as SpO2 or heart rate (HR). However, the PPG optical sensor configuration and component choice can influence the accuracy and signal reliability. This study investigates the combined influence of LED viewing angles and optical windows (protective glass) on the PPG signal quality. In order to eliminate the influence of other factors, synthetic PPG signals (WhaleTeq AECG100) serve as the signal source. The experimental design evaluates the impact of wide- vs narrow-angle LEDs, along with different optical window choices (material composition, thickness, and coating). Signal quality metrics and statistical tools are employed for analysis. The results improve LED and optical window selection for enhanced PPG signal acquisition.

In this study, we present a label-free fiber optic plasmonic aptasensor to detect undesirable biomolecules in agriculture and fisheries. The biomolecules may lead to bad food production and quality. We used a small homemade cuvette, a 50 kD membrane, and a mirror, which are attached to the tip of the optical fiber to hold a sensing assay. We demonstrate real-time binding of biomolecules using aptamer capture chemistry. We present a new compact design with many benefits, such as easy chemical/physical surface immobilization and the possibility of a high assay density in front of the fiber tip. Acknowledgement: This work has received funding from VILLUM FONDEN (Villum Investigator project Table-Top Synchrotrons, No. 00037822) and Green Development, and Demonstration Program under the Danish Ministry for Food, Agriculture and Fisheries (GeoZense, 34009-20-1769).

In this paper, we report the fabrication of optical fibre sensors functionalised with metal-organic frameworks MFM-101 for the detection of the anaesthetic drug propofol. The deposition of MFM-101 onto optical fibres was analysed in real-time via UV-Vis spectroscopy to assess the differences between functionalisation and deposition methods. Initial results of exposure of coated optical fibre sensor to different concentrations of propofol will be reported. The effect of surface functionalisation methods of the optical fibre on the structure of the deposited MFM-101 has been investigated. Preliminary results show the potential of application-developed sensors for propofol detection in the gas phase.

In this study, we fabricated cholesteric liquid crystal elastomers (CLCEs) that operate in the NIR region. Based on this device, we confirmed the change in polarization state of the reflector with pitch change and its deformation with uniaxial tension application. To measure the reflection characteristics of CLCE in a wide wavelength range, a broadband wavelength-swept laser was used as a light source. It was confirmed that when CLCE was applied with a tension of about 100 to 160%, the reflection band continuously shifted to a shorter wavelength. In addition, to confirm the reflection characteristics according to the deformation of CLCE, the transmission spectra of the left and right circular polarization and linear polarization states of the incident beam were compared when tensile force was applied.