In-line Fiber Research Articles

Plasmon-assisted fiber polarizers with high extinction ratio and low insertion loss

We propose a compact plasmon-assisted in-line fiber polarizer with metal films selectively coated on the lateral surface of the cladding in a conventional single mode fiber. The polarization-dependent loss mechanism intrinsically originates from the polarization-selective excitation of surface plasmon polaritons (SPPs) at both interfaces of metal films. Both the polarization extinction ratio (PER) and insertion loss (IL) of the plasmonic fiber polarizer strongly depend on the strength of the interaction between the polarized core modes and SPP modes. We numerically demonstrate the performances of an Au-coated and an Al-coated fiber polarizers, respectively. Both of them can achieve a PER at least higher than 10 dB/mm over the whole C- and L-bands. Notably, the PERs at 1550 nm in the Au-coated and Al-coated fiber polarizers can be up to 37.3 dB/mm and 29.4 dB/mm, respectively. The IL in the Al-coated fiber polarizer is about an order of magnitude higher than that in the Au-coated one, but it can still be lower than 0.1 dB/mm over the C- and L-bands. The achievable excellent performance shows that our proposed plasmonic fiber polarizer can provide a promising candidate for compact all-fiber polarizers with a high PER and a low IL.

Optical curvature sensor with high resolution based on in-line fiber Mach-Zehnder interferometer and microwave photonic filter.

Curvature measurement plays an important role in structural health monitoring, robot-pose measuring, etc. High-resolution curvature measurement is highly demanded. In this paper, an optical curvature sensor with high resolution based on in-fiber Mach-Zehnder interferometer (MZI) and microwave photonic filter (MPF) is proposed and experimentally demonstrated. The in-fiber MZI is constructed with a ring-core fiber (RCF) which is fusion spliced between two coreless fibers (CLFs). The structure of CLF-RCF-CLF is then sandwiched between two segments of single-mode fiber (SMF), making the whole interferometer structure of SMF-CLF-RCF-CLF-SMF. The operating principle is that different curvatures will cause the variations of the interference spectrum of MZI due to elastic-optic effect, and then the variations are converted into the frequency-shift of the MPF. The factors affecting the visibility of the interference spectrum are researched. A preliminary exploration of the multiplexing demodulation for the in-fiber-MZIs is also investigated and discussed, which is for the first time to the best of our knowledge, holding great potential to pave the way for constructing the sensing network composed of interferometric sensors. The curvature measurement sensitivity is -147.634 MHz/m-1, and the resolution is 6.774 × 10-6 m-1 which is the highest value up to now.

Hemp From Disordered Lines for New Staple Fibre Yarns and High-Performance Composite Applications

The use of natural fibre-reinforced plastics for higher-stressed applications is currently often limited by the high price of high-quality semi-finished products. Therefore, the present study deals with developing yarns from cost-effective hemp from a disordered separation process (total fibre line) for composite reinforcements. Composites were fabricated using a miniature pultrusion process with thermosetting matrices from the yarns. The results show that around 90% of the flexural strength and flexural modulus of identically produced flax composites could be achieved with maximum values of 282 MPa for the flexural strength and 23.4 GPa for the flexural modulus. The yarns were additionally used to manufacture quasi-unidirectional fabrics to produce composite laminates using different manufacturing processes. The highest values were obtained for a laminate with 39 vol% fibre content, produced with a resin injection process in an autoclave, achieving a tensile strength of 155 MPa, Young’s modulus of 19.4 GPa, a flexural strength of 174 MPa and bending modulus of 12.4 GPa. The characteristic values are sufficient to use the materials in applications with higher mechanical requirements.

Macro-strain based deflection and neutral axis position monitoring of reinforced concrete beams during corrosion

This article proposes a new technique of monitoring neutral axis positions and deflection of Reinforced Concrete (RC) beam during corrosion of steel reinforcement using macro-strain measurements of distributed long-gauge sensors. A different group of distributed long-gauge Packaged Carbon Fiber Line (PCFL) sensors with self-compensation and effective packaging system is installed on the compression and tension fibers of the concrete surface and steel reinforcements of RC beam to verify the proposed method experimentally. An accelerated corrosion method utilizing a salt solution and the constant current was used to achieve the required corrosion levels. The estimated deflection measured by the developed method is compared with the results using Linear Variable Displacement Transducer (LVDTs). It has been demonstrated that long-gauge PCFL sensors could provide the same accuracy. The distributed measured strains were utilized to evaluate the deterioration of the structure’s health with the advance of corrosion. Based on corrosion monitoring experimental results, it can be confirmed that using distributed PCFL sensors mounted on steel reinforcements or concrete surface, the locations and progress of the damage with corrosion time can be detected effectively. The maximum error in the estimated deflection from PCFL sensors mounted on the concrete surface compared to the LVDTs before the onset and after 24 h of accelerated corrosion was 0.5% and 2.5%, respectively.

Design and Implementation of the Illinois Express Quantum Metropolitan Area Network

The Illinois Express Quantum Network (IEQNET) is a program to realize metropolitan scale quantum networking over deployed optical fiber using currently available technology. IEQNET consists of multiple sites that are geographically dispersed in the Chicago metropolitan area. Each site has one or more quantum nodes (Q-nodes) representing the communication parties in a quantum network. Q-nodes generate or measure quantum signals such as entangled photons and communicate the measurement results via standard, classical signals and conventional networking processes. The entangled photons in IEQNET nodes are generated at multiple wavelengths, and are selectively distributed to the desired users via transparent optical switches. Here we describe the network architecture of IEQNET, including the Internet-inspired layered hierarchy that leverages software-defined networking (SDN) technology to perform traditional wavelength routing and assignment between the Q-nodes. Specifically, SDN decouples the control and data planes, with the control plane being entirely implemented in the classical domain. We also discuss the IEQNET processes that address issues associated with synchronization, calibration, network monitoring, and scheduling. An important goal of IEQNET is to demonstrate the extent to which the control plane classical signals can co-propagate with the data plane quantum signals in the same fiber lines (quantum-classical signal "coexistence"). This goal is furthered by the use of tunable narrow-band optical filtering at the receivers and, at least in some cases, a wide wavelength separation between the quantum and classical channels. We envision IEQNET to aid in developing robust and practical quantum networks by demonstrating metro-scale quantum communication tasks such as entanglement distribution and quantum-state teleportation.

Comparison Of Yield and Fiber Properties by Correlation, Biplot and Cluster Analysis in Some Cotton (Gossypium Hirsutum L.) Hybrids

Cotton is the most important fiber crop. Seed cotton yield, ginning outturn, lint yield, some fiber quality parameters and adaptation capability of eleven hybrid (F5-6) cotton genotype were assessed in this study at Antalya/Türkiye conditions. The study was conducted in a randomized block design with three replications in 2017 and 2018. The level and significance of the relationships between genotype-traits and traits were determined by correlation, biplot and cluster analysis. Resulting, hybrid lines which 1102 for seed cotton yield and fiber yield, 1008 for seed cotton yield, ginning outturn and fiber yield, 1019 and 1103 for all the characters and Gloria cultivar for fiber parameters were significant. In addition, hybrids which line 1115 for seed cotton yield, fiber yield, spinning consistency index and fiber maturity, lines 1005, 1006, 1101, 1102, 1105 and Sure Grow 125 cultivar were found insignificant due to their high short fiber content. The fiber yield showed significant and positive correlation with seed cotton yield, ginning outturn, fiber maturity and fiber fineness, which were not affected by the year difference. The spinning consistency index determined by the combination of a plurality of fiber properties, it has always been found to have very important and positive correlation with fiber length, fiber strength and fiber uniformity index, negligible but positive with ginning outturn, whereas short fiber index was always significantly and negatively correlated.

Fiber-Extended Copper Line Architecture With End-to-End Data Transmission and Link Monitoring

We demonstrate a prototype hybrid, full duplex fiber-extended copper line with frequency-reusability and simultaneous fiber and copper line monitoring. The link architecture is composed of three main units: a central office; a remote-node copper to fiber converter (CuFiC); and a radio head. A fiber optical link connects the central office to the remote node, while the remote node is connected to the radio head by a copper line. Even though the prototype is built with two full duplex channels, more channels can be supported by the architecture, and an optical feedforward linearization scheme for the transmitter is demonstrated for that purpose. In-service simultaneous multi-copper and fiber monitoring is possible with the right choice of frequency bands, a result backed by the Error Vector Magnitude measurement of data channels in simultaneous coexistence with monitoring channels. A frequency multiplication unit, built into both the transmitter and the remote node, allows for a single seed tone to generate all the sub-carrier multiplexed channels for up and downstream in both the fiber and in the copper links without the need of local oscillators. This not only simplifies the architecture, but also allows for optimal homodyne up- /down-conversion. The demonstrated prototype figures as a potential candidate for interfacing fiber to the home and fiber to the building (FTTH/FTTB) links with legacy copper infrastructure currently allowing for: up to eight 20MHz LTE 64QAM channels to be subcarrier-multiplexed onto a single optical carrier and seemlessly demultiplexed into individual copper channels, backed by a ≤8% EVM measured at the radio head; concurrent 7dB dynamic range 10 meter spatial resolution intermediate-haul fiber monitoring (up to 15 km) as well as copper line monitoring both available at the central office. The next steps beyond the presented proof of concept include simultaneous bi-directional transmission among multiple receivers, automated feed-forward linearization, and the study of factors that may limit the achievable dynamic range.

Field trial of 24-Tb/s (60 × 400Gb/s) DWDM transmission over a 1910-km G.654.E fiber link with 6-THz-bandwidth C-band EDFAs

We demonstrate real-time 24-Tb/s dense wavelength division multiplexing (DWDM) transmission over a 1910-km field-deployed G.654.E fiber link using 24 in-line wide-bandwidth Erbium-doped fiber amplifiers with a widened bandwidth of 6 THz in the cost-effective C-band. The DWDM system consists of 60 100-GHz-spaced 400-Gb/s wavelength channels, modulated with probabilistic constellation shaped polarization-division-multiplexed 16-point quadrature-amplitude modulation and fast-than-Nyquist shaping. This field trial shows the feasibility of achieving a record per-fiber capacity of 24 Tb/s in field-deployed 2000-km-class terrestrial fiber links by using the widened C-band.

Organization of the technological process of hemp treatment processing with chaotic arrangement of stems at the hemp plant

The aim is to study the possibilities of processing hemp with a chaotic arrangement of stems on the technological equipment of a hemp plant, to determine the quality indicators of the produced fiber. A brief description of the work performed. The technological processes of processing hemp with a chaotic arrangement of stems on the equipment of hemp growers with the separation of the fiber into long and short and its receipt in the total mass were studied. It was established that during the processing of this raw material on a milling and heating unit, the produced long fiber has a low yield of 6 to 11%, depending on the characteristics of the trust in a roll with its length from 110 to 160 cm. Its production is carried out with frequent stops of the technological process with the reasons why a significant part of the stems do not fall under the clamp of the transporting conveyor, which cause clogging of the pneumatic conveying system. At the same time, about two-thirds or more of the total mass is short fiber. With such obtained indicators, the production of a long fiber from a trust with a chaotic arrangement of stems is impractical. When producing hemp fiber in the total mass on the equipment of the hemp grower, the gear-type ball forming mechanism is excluded from the technological process, and the raw material after passing is transferred to the short fiber line by the pneumatic transport system through the inspection window of the first section of the heating drums when they are turned off. The produced fiber in total weight can mostly correspond to the second or third grade depending on its breaking load. Conclusions. The possibilities of processing hemp with a chaotic arrangement of stems on the technological equipment of the hemp plant and indicators of the quality of the produced fiber are determined.

Temperature dependence of a refractive index sensor based on a bent core-offset in-line fiber Mach-Zehnder interferometer

A bent core-offset in-line fiber Mach-Zehnder Interferometer (MZI) as a refractive index (RI) sensor was fabricated by using a commercial fusion splicer. The temperature dependence on the so-obtained sensor was investigated. It showed that not only the RI sensitivity, but also the temperature sensitivity could be enhanced by reducing the bending radius. The variation of RI and the temperature hardly affected the sensitivity of each other within the margin of error. The wavelength-related measurement was used to realize the simultaneous measurement of RI and temperature. The highest temperature sensitivity of 0.11745 nm/°C and the highest RI sensitivity of −115.5646 nm/RIU was obtained by the sensor with a length of 30 mm, a core-offset of 6 µm, and a bending radius of 25.42 mm.

COMBINED NEURAL NETWORK METHOD FOR DETERMINING THE BRILLOUIN SPECTRUM MAXIMUM IN DISTRIBUTED FIBER-OPTIC SENSORS

Distributed fiber-optic sensors are becoming an increasingly common solution for monitoring and diagnosing extended information transmission lines, industrial devices, buildings and devices. One of the directions – Brillouin reflectometry, which allows diagnosing a fiber line for changes in ambient temperature or mechanical deformation, is becoming increasingly popular for engineers and researchers. However, modern standards impose increasingly strict requirements on diagnostic systems in terms of the accuracy of determined parameters. For Brillouin reflectometry, where the value of the environmental parameters is determined by the position of the maximum of the Brillouin gain spectrum, the task of more accurately determining this maximum becomes the main one. The paper considers modern computer-computational methods for detecting the maximum of the Brillouin gain spectrum in an optical fiber. The authors note that imperfections in the shape of the optical spectrum, such as the signal-to-noise ratio, as well as possible digital defects that occur during digitization, can significantly impair the accuracy of the system. The authors consider three approaches to detecting the maximum of the spectrum: the classical method of Lorentz curve fitting, the method of cross-correlation with the ideal Lorentzian function, as well as the method of inverse correlation developed by the authors earlier. To combine the results of the work of the three methods, a neural network model was developed that accepts the input data of each method, together with the parameters of noise and distortion of the spectrum. The model is presented in the form of a four-layer perceptron with two hidden layers. As a result, the authors achieved an increase in the accuracy of determining the position of the maximum of the spectrum by 10% on the model data.

Development of novel anisotropic skin simulants

Skin tissues are anisotropic, and their mechanical characteristics vary widely depending on where they are located on the body. While some research has been conducted in the past to numerically model tissue anisotropy, anisotropic skin simulants have not been developed yet. In this work, a soft composite-based framework was employed to fabricate such simulants. Stiffer polymeric fibers were embedded in a softer polymeric matrix to generate a wide range (n = 155) of one- and two-layer skin simulants with uniform fiber volume fraction (FVF) and fiber spacings, and varying fiber orientations. Variants with different curvatures of Langar fiber lines were also simulated to study their properties. Mechanical tests were conducted to estimate the stress-stretch responses, which were compared with natural skin properties, and further characterized using isotropic and anisotropic hyperelastic formulations. The developed anisotropic skin simulants would be indispensable for accurate biomechanical testing of skin without any ethical and biosafety concerns, surgical training, and evaluation of medical interventions.

Muscle Fiber Contribution to Rotator Cuff Moment Arms During Abduction for Intact Rotator Cuff, Complete Supraspinatus Tear, Superior Capsular Reconstruction, and Reverse Shoulder Arthroplasty. (225)

Objectives:The Rotator Cuff (RC) is formed from the subscapularis, supraspinatus, infraspinatus, and teres minor muscles and their tendinous extensions. The 4 RC tendons insert on the humeral head such that they contribute to the dynamic stability of the glenohumeral joint along with their rotational actions on the shoulder. The moment arm can be used to demonstrate the work effort potential that a specific muscle is contributing to a musculoskeletal joint rotation. The objective of this study was to break out RC muscles into multiple fibers, providing more clarity as to how individual fibers contribute to a muscle’s overall moment arm during abduction.The aims of this study are: 1.) to illustrate within each RC muscle how multiple muscle fiber lines of action work together to produce abduction in an intact shoulder 2.) to estimate the moment arm changes that take place when the intact rotator cuff goes through surgical repair with either SCR or RSA after complete supraspinatus tear. We hypothesized that the rotator cuff muscles work differently and in combination at the fiber level to bring about a resultant movement that can be assessed through the proposed method of moment arm calculation for intact RC, complete supraspinatus tear, SCR and RSA.Methods:Five fresh cadaveric shoulder specimens were used in an apparatus where each muscle was maintained in tension with the line of action towards its origin on the scapula (Figure 1). An Optotrack camera kept track of digitized points along both the origin and insertion of the rotator cuff muscles as the shoulder was abducted. Using these digitized points, multiple lines of action were created across the breadth of each muscle. Each muscle force action line was then used to calculate moment arm values during 0-90º abduction (Figure 2).Results:Moment arms calculated for multiple fiber lines spanning the tendon attachment site displayed the variance of fiber contribution and function within each muscle during abduction. Our results indicate that rather than providing a return to anatomical shoulder muscle function, RSA and SCR models produce moment arms that vary between muscles, with some contributing more to abduction and some contributing less. Highlighted below are the infraspinatus results for moment arms of individual fiber lines of action (Figure 3) and calculated mean moment arms (Figure 4) over abduction.ANOVA testing demonstrated a significant difference (p<0.001) when analyzing moment arms of intact, complete supraspinatus tear, SCR, and RSA models in teres minor and infraspinatus. There was no significant difference in moment arm values between the models in the subscapularis (p=0.148). Highlighted in Table 1 are the ANOVA testing results for infraspinatus.Conclusions:Our biomechanical analysis demonstrated sufficient sensitivity to detect differences in moment arms of the four rotator cuff muscles across a variety of models, suggesting changes to even one muscle of the shoulder will have significant implications on the function of other shoulder muscles. Furthermore, our analysis of fiber divisions within the same muscle illustrates the complex nature of the shoulder muscles themselves, and future studies should aim to better explore and model their function. The calculated percent differences from intact beautifully illustrated this complexity, as corrective RSA and SCR procedures provided better resemblance of intact anatomy within some rotator cuff muscles while creating a larger percent difference in other muscle groups.By breaking out RC muscles into multiple fibers, more clarity can be gained as to how individual fibers contribute to a muscle’s overall moment arm during abduction. This may further aid surgical decision-making, specifically for RSA where there is continued debate about whether to reconstruct portions of the RC. Given that the supraspinatus tendon is the most frequently torn tendon in the rotator cuff, especially for athletes who apply repetitive stress to the tendon, the results of this study may help inform post-operative rehabilitation by illustrating how abduction and stability are achieved after SCR and RSA.

Optical Fiber In-Line Mach-Zehnder Interferometer Based On an Inner Air-Cavity With Long Cavity Length

An optical fiber in-line Mach-Zehnder interferometer based on an inner air-cavity with long cavity length is demonstrated. The device is fabricated by using femtosecond laser to inscribe a waveguide structure in the optical fiber core, followed by discharging the waveguide area with a fusion splicer. The inner air-cavity structure is highly robust, and the relatively long cavity length corresponds to a small free spectral range, which makes it possible to implement accurate measurement. Such an inner air-cavity device fabricated in single mode fiber has good high temperature sustainability. The device is also “open” to the external environment when being fabricated in multimode fiber, thus supporting refractive index measurement. The proposed device is attractive in many optical fiber sensing applications.

Utilizing thermally induced selective mode shaping for a high extinction ratio in-line fiber modulator/polarizer.

Light-matter interactions of guided modes strongly depend on mode shape. This Letter presents an ultrahigh extinction ratio (ER) polarizer/modulator at λ=1.55µm, enabled by selective mode reshaping for different orthogonal modes. This bi-function device benefits from a designed side-polished fiber (SPF) with a three-layer stack of graphene/VO2/PMMA overlay. Thermally induced insulator-metal transition (IMT) in VO2 via a graphene microheater leads to the polarization-selective mode shaping (PSMS), which is used to manipulate orthogonal modes separately. As a result, a TE modulator (TM-pass polarizer) with an ultrahigh ER=168.4dB/mm (175.1 dB/mm) and low insertion loss (IL) of IL=3.38dB/mm (0.34 dB/mm) is achieved.

Ultrasensitive Refractive Index Sensor Based on Mach–Zehnder Interferometer and a 40μm Fiber

An ultra-high sensitivity refractive index (RI) sensor, based on an in-line fiber Mach-Zehnder interferometer (MZI) and utilizing a special 40 μm fiber which has been specifically designed for the purpose, supporting only the LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes propagating in the fiber, has been proposed and numerically demonstrated in this work. The all-fiber MZI, based on LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode interference, was fabricated by utilizing a special design with two gradually tapered joints at both sides of this multi-clad thin diameter fiber (TDF). When the TDF diameters varied from 40 μm to 5 μm, a sudden change in the direction of the wavelength shift in the transmission spectrum of the TDF-MZI devices was observed both in liquid RI and air relative humidity (RH) monitoring experiments, as the surrounding RI or RH was seen to increase monotonically. Ultra-high sensitivity values of 5942.8nm/RIU (1.335-1.342) and 21292.2nm/RIU (1.4000-1.4025) were obtained in the experiments carried out, through the use of a tapered TDF-MZI device with TDF diameters of ~5 μm and ~9 μm, respectively. The maximum RH sensitivity of 1.084nm/%RH was obtained by the use of the TDF-MZI device with a TDF diameter of ~12 μm. A compact all-fiber TDF-MZI sensor was thus created with an overall sensing length of <; 4mm, showing the advantages of high sensitivity, low loss, and flexibility in the tunable monitoring direction of the wavelength shift. This design is well suited to various applications, where the high sensitivity RI and RH measurements are required at precise locations.

Evolution of pectin synthesis relevant galacturonosyltransferase gene family and its expression during cotton fiber development

BackgroundPectin is a key substance involved in cell wall development, and the galacturonosyltransferases (GAUTs) gene family is a critical participant in the pectin synthesis pathway. Systematic and comprehensive research on GAUTs has not been performed in cotton. Analysis of the evolution and expression patterns of the GAUT gene family in different cotton species is needed to increase knowledge of the function of pectin in cotton fiber development.ResultsIn this study, we have identified 131 GAUT genes in the genomes of four Gossypium species (G. raimondii, G. barbadense, G. hirsutum, and G. arboreum), and classified them as GAUT-A, GAUT-B and GAUT-C, which coding probable galacturonosyltransferases. Among them, the GAUT genes encode proteins GAUT1 to GAUT15. All GAUT proteins except for GAUT7 contain a conserved glycosyl transferase family 8 domain (H-DN-A-SVV-S-V-H-T-F). The conserved sequence of GAUT7 is PLN (phospholamban) 02769 domain. According to cis-elemet analysis, GAUT genes transcript levels may be regulated by hormones such as JA, GA, SA, ABA, Me-JA, and IAA. The evolution and transcription patterns of the GAUT gene family in different cotton species and the transcript levels in upland cotton lines with different fiber strength were analyzed. Peak transcript level of GhGAUT genes have been observed before 15 DPA. In the six materials with high fiber strength, the transcription of GhGAUT genes were concentrated from 10 to 15 DPA; while the highest transcript levels in low fiber strength materials were detected between 5 and 10 DPA. These results lays the foundation for future research on gene function during cotton fiber development.ConclusionsThe GAUT gene family may affect cotton fiber development, including fiber elongation and fiber thickening. In the low strength fiber lines, GAUTs mainly participate in fiber elongation, whereas their major effect on cotton with high strength fiber is related to both elongation and thickening.

Chemically Functionalised Suspended-Core Fibre for Ammonia Gas Detection

An optical fibre ammonia gas sensor utilising a functionalised four-leaf-clover-shaped suspended-core fibre (SCF) is demonstrated. The fibre is functionalised by depositing a thin layer of an ammonia sensitive dye (tetraphenylporphyrin tetrasulfonic acid hydrate) (TPPS) on the wall of the inner cavities of the SCF through capillary action. An in-line fibre sensing structure is designed for light transmission through the SCF and also allows gas exchange with the atmosphere through two porous polyethylene housings. The sensing structure exhibits a temperature-dependent transmission due to the thermal expansion of the housings. A ratiometric method is applied for signal processing which is demonstrated to reduce significantly the effect of temperature change in the tested range (20-30 °C). The sensor is tested in ammonia concentration ranges from 0-10 ppm and demonstrates capability of detecting ammonia at ppb levels. The minimum tested concentration is 150 ppb in the experiment with a calculated limit of detection of 20 ppb. The sensor response time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10-90%</sub> ) is 160 s and it is demonstrated to be reusable after treatment with hydrogen chloride vapour. Numerical simulation of evanescent absorption features of such an SCF indicates that approximately 0.02% of the optical power exists in the air holes for the fundamental propagation mode. Distinctive absorption bands observed in the transmission spectrum of the fabricated sensor can also be observed in the simulated model after adding the TPPS absorption layer in the holes.

Lab on optical fiber: surface nano-functionalization for real-time monitoring of VOC adsorption/desorption in metal-organic frameworks

Abstract Metal-organic framework (MOF) nanomaterials are emerging porous coordinative polymers with large surface area and high porosity. Their application scenarios highly depend on adsorption/desorption dynamics of guest molecules in the framework. For representative ZIF-8 with framework flexibility, the study of molecule transportation in the pore channels of ZIF-8 will address the ambiguity of unclear application scenarios. In this study, the integration of lab-on-fiber technology and nanotechnology are demonstrated for real-time monitoring of adsorption/desorption dynamics of heterocyclic volatile compounds (VOCs) with kinetic diameters larger than the window aperture of ZIF-8. The in-line fiber interferometer with cascaded long-period gratings is used to monitor the real-time refractive index change of VOC adsorption/desorption. The structure-effect relationship between guest VOCs and framework flexibility is analyzed. It shows that the adsorption dynamics is highly related to the molecular geometry and kinetic diameter. The framework flexibility results in the trapping of guest VOCs toluene, pyridine, and tetrahydrofuran in the frameworks. The methanol adsorption/desorption is an effective strategy for the fast desorption of trapped residual VOCs in the framework. Finally, we conceptually demonstrated the real-time monitoring of trace toluene enrichment using ZIF-8 for indoor air purification. This study paves the way for the in-depth understanding of framework flexibility for MOF’s application.

Trace copper detection using in-line optical fiber Mach-Zehnder interferometer combined with an optoelectronic oscillator.

We experimentally demonstrate a novel optical fiber chemosensor for trace Cu2+ ions detection that is implemented by using an in-line optical fiber Mach-Zehnder interferometer (MZI) in conjunction with an optoelectronic oscillator (OEO). The MZI is fabricated by lateral offset splicing a section of D-shaped fiber between two single-mode fibers. It splices the broadband optical source into a sinusoidal-shaped light, which can form a single passband microwave photonic filter (MPF) by combining the Mach-Zehnder modulator, a segment of fiber and a photodetector. The center frequency of the MPF, determined by the free spectra range of MZI, is affected by the solution concentration. Incorporating the MPF in the OEO sensor, the oscillation frequency is determined by the solution concentration. Therefore, we can estimate the solution concentration by measuring the microwave frequency change. We carry out a proof to concept experiment. High sensitivity Cu2+ ions concentration sensing with sensitivity of 13 Hz/(μM/L) is achieved. The maximum measurement error of concentration obtained is within 1.38 μM/L. The proposed sensor has merits of high interrogation speed, simple operation, high sensitivity and accuracy, offering the potentials in a wide range of biological application scenarios.