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The paper presents historical perspective of fibre-optic seismographs designed and constructed at the Institute of Applied Physics at Military University of Technology, Poland based on the so-called minimum configuration of fibre-optic gyroscope. The briefly presented history, which originated in the 1998 by the system named GS-13P, laid solid foundations for the construction of a three-axis fibre-optic seismograph. The presented system meets all technical requirements of rotational seismology in terms of measurement parameters (measuring range from 10−8 rad/s to several rad/s and frequency from 0.01 Hz to 100 Hz) and utility features (mobility, autonomy, power independence, environmental stability). The presented device provides universal application both for research in engineering applications (high buildings, chimneys, wind towers) as well as in seismological research. [ABSTRACT FROM AUTHOR]

Starting with descriptions of rotational seismology, areas of interest and historical field measurements, the fundamental requirements for rotational seismometers for seismological and engineering application are formulated. On the above basis, a review of all existing rotational seismometers is presented with a description of the principles of their operation as well as possibilities to fulfill formulated requirements. This review includes mechanical, acoustical, electrochemical and optical devices and shows that the last of these types are the most promising. It is shown that optical rotational seismometer based on the ring-laser gyroscope concept is the best for seismological applications, whereas systems based on fiber-optic gyroscopes demonstrate parameters which are also required for engineering applications. Laboratory results of the Fibre-Optic System for Rotational Events & Phenomena Monitoring using a small 1-D shaking table modified to generate rotational excitations are presented. The harmonic and time-history tests demonstrate its usefulness for recording rotational motions with rates up to 0.25 rad/s. [ABSTRACT FROM AUTHOR]

We outline the development and the application in a field test of the Autonomous Fibre-Optic Rotational Seismograph (AFORS), which utilizes the Sagnac effect for a direct measurement of the seismic-origin rotations of the ground. The main advantage of AFORS is its complete insensitivity to linear motions, as well as a direct measurement of rotational components emitted during seismic events. The presented system contains a special autonomous signal processing unit which optimizes its operation for the measurement of rotation motions, whereas the applied telemetric system based on the Internet allows for an AFORS remote control. The laboratory investigation of such two devices indicated that they keep an accuracy of no less than 5.1 x 10-9 to 5.5 x 10-8 rad/s in the detection frequency band from 0.83~106.15 Hz and protect linear changes of sensitivity in the above bandpass. Some experimental results of an AFORS-1 application for a continuous monitoring of the rotational events in the Książ (Poland) seismological observatory are also presented. [ABSTRACT FROM AUTHOR]

This paper presents a study of the influence of bimetallic layer covers of a tapered optical fiber surrounded by a low refractive index liquid crystal on the properties of light propagation in the taper structure. This research follows previous works on the effect of monometallic thin films (Au and Ag). In this case, the total thicknesses of the bimetallic layers were h = 10 nm, and the participation of gold and silver was equal. The films were deposited on one side of the tapered waist area. The liquid crystal cells were controlled with a voltage U from 0 to 200 V, with and without amplitude modulation at a frequency of fmod = 5 Hz. For the purposes of this research, spectral characteristics were obtained for a wavelength λ ranging from 550 to 1200 nm. Measurements were carried out at room temperature for three types of rubbed layers orientation—orthogonal, parallel, and twist in relation to the fiber axis. Obtained resonant peaks were compared with the previous results regarding the resonant wavelength, peak width, SNR, and maximum absorption. In the presented paper, the novelty is mainly focused on the materials used and their time stability, as well as corresponding changes in the technological parameters used. [ABSTRACT FROM AUTHOR]

In the paper new areas of the fiber-optic Sagnac interferometer applications are discussed and proposed. Because this system detects the absolute rotation, its application is directly designed for detection of the seismic rotation waves which are rotational events existing in the seismic waves. In most cases those waves are extracted from recordings of differential seismic signals. However, all differences in responses of the seismometers cause disturbances which obscure these hidden components as it is for two antiparallel pendulum seismometers (TAPS) system. The presented device, named fiber-optic rotational seismometer (FORS), is free from this disadvantage and may be used for other rotational seismometer calibration, as well as for direct seismic rotation waves detection. The paper describes the design based on a well-known optical gyroscope configuration but with its optimization for its optimization for detection the absolute rotation, only. The obtained results have been the source of TAPS work improvement by applying the data smoothing by a spline function. Moreover, the first application of FORS for recording rotational parts existing in the seismic events has shown that they probably propagate with different velocity than classical earthquake waves. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to description of the partial polarization in a fiber-optic system. The introduced mode! is treating depolarization as a distribution of different states of polarization (SOP). The parameters of such SOP distribution function are connected with the spectral character of a light source, which may give a depolarization process different from a linear one in an optical fiber system. Such description of light propagation in an optical fiber can be useful for investigation of the polarization mode dispersion. This paper also presents results of the degree of polarization measurement by application of the introduced approach in the fiber-optic interferometric polarization analyzer. This is the fiber-optic Sagnac interferometer which uses a measurement technique based on the fourth Fresnel-Arago's condition of polarized beam interference. [ABSTRACT FROM AUTHOR]

Measurements of artificial events can substantially confirm the data validity of constructed rotational sensors, as well as provide methods for simplifying the measurement process. The above task, especially with international cooperation, can provide full-field measurement results of the target object, which can deliver more significant data and sensor properties. The paper presents vertical rotational velocity recordings gathered during an international experiment that took place at the Geophysical Observatory of the Ludwig Maximilian University of Munich in Fürstenfeldbruck, Germany. Data were obtained during artificial explosions, as well as external excitations induced by a VibroSeis truck. The authors present data recorded by two prototypes of optical fiber rotational sensors. They have been specially designed for rotational seismology needs and are characterized by a theoretical sensitivity equal to 2 × 10−8 rad/s/√Hz and a wide measuring range both in amplitude even up to 10 rad/s, and a frequency from DC to 1000 Hz. Their self-noise investigation during the aforementioned experiment showed that both sensors have precision no worse than 2 × 10−6 rad/s/sqrt (Hz) in all desired frequency range from 0.01 to 100 Hz. A down-sampling and a spectral analysis of the recorded signals are also presented. The recorded data and their analysis confirmed the performance and reliability of the applied optical fiber rotational sensors. Moreover, the presented international experiment underlines a special necessity for specifying the sensors' performance test methodologies in the rotational seismology. [ABSTRACT FROM AUTHOR]

This article proposes an interferometric method for a variable depolarizer characterization with features that distinguish it from the polarimetric system. Information about the behavior of a vertically aligned nematic cell as a variable depolarizer can be extracted from Young interferometer measurements in real time. These results could be significant for understanding the polarization phenomena in depolarizing media such as biological tissue. [ABSTRACT FROM AUTHOR]

The paper presents construction and laboratory tests, as well as the first field application of a new fiber-optic rotational seismograph. The system is based on a fiber-optic gyroscope (FOG), with determined Angle Random Walk of the order of 10−8 rad/Sqrt(s) and a few rad/s maximum detectable amplitude of rotation in the frequency range from direct current (DC) to 328.12 Hz. It has been designed for the rotational seismology area of interest. This work also presents exemplary relevant measurements, which were conducted using a set of two devices installed in the geophysical observatory in Książ, Poland. [ABSTRACT FROM AUTHOR]

The proper classification of the origins of food products is a crucial issue all over the world nowadays. In this paper, the authors present a device—a multispectral portable fibre-optic reflectometer and signal processing patch—together with a machine-learning algorithm for the classification of the origins of chicken eggshells in the case of Mycoplasma synoviae infection. The sensor device was developed based on previous studies with a continuous spectrum in transmittance and selected spectral lines in reflectance. In the described case, the sensor is based on the integration of reflected spectral data from short spectral bands from the VIS and NIR region, which are produced by single-colour LEDs and introduced to the sample via a fibre bundle. The measurement is carried out in a sequence, and the reflected signal is pre-processed to be put in the machine learning algorithm. The support vector machine algorithm is used together with three different types of data normalization. The obtained results of the F-score factor for classification of the origins of samples show that the percentages of eggs coming from Mycoplasma synoviae infected hens are up to 87% for white and 96% for brown eggshells. [ABSTRACT FROM AUTHOR]

Modern optoelectronic devices use the advantage of digital systems for data processing aimed at delivering reliable information. However, since commonly used DACs have limited accuracy, some artefacts can be observed in data streams, especially in systems designed for continuous, long-term process monitoring. In this paper, the authors' experience with data enhancement using a fibre-optic rotational seismograph (FORS) operating in a closed-loop mode is presented and discussed. Generally, two kinds of enhancement are described. The first one uses suitable filtering techniques adequate for FORS noise investigation, as well as a suitable data resampling method for transmitted data file size reduction. The second one relates to the artefacts observed during data recording in real time. The recording starting point is triggered when the detected signal exceeds a middle signal level and, therefore, the existence of artefacts generally disturbs the recording process. Although the artefacts are easily recognised by human eyes even at first sight, their automatic elimination is not so easy. In this paper, the authors propose a new concept of signal filtering to solve the above problem. [ABSTRACT FROM AUTHOR]

The presented research shows the possibilities of creating in-line magnetic sensors based on the detection of changes of light propagation parameters, especially polarization, obtained by mixing Fe3O4 nanoparticles with hexadecane (higher alkane) surrounding a biconical optical fiber taper. The fiber optic taper allows to directly influence light parameters inside the taper without the necessity to lead the beam out of the structure. The mixture of hexadecane and Fe3O4 nanoparticles forms a special cladding surrounding a fiber taper which can be controlled by external factors such as the magnetic field. Described studies show changes of transmission (power, loss) and polarization properties like azimuth, and ellipticity, depending on the location of the mixture on sections of tapered optical fiber. The taper was made of a standard single-mode telecommunication fiber, stretched out to a length of 20.0 ± 0.5 mm and the diameter of the tapers is around 15.0 ± 0.3 μm, with the loss lower than 0.5 dB @ 1550 nm. Such a taper causes the beam to leak out of the waist structure and allows the addition of the external beam-controlling cladding material. The presented research can be used to build polarization switches or optical sensor. The results show that it can be a new way to control the propagation parameters of a light beam using tapered optical fiber and magnetic mixture. [ABSTRACT FROM AUTHOR]

Abstract: Four types of photonic crystal fibres (PCFs) with different structures and values of birefringence have been evaluated and cross-compared in terms of their corresponding characteristics and sensitivities to lateral force (or pressure), considering this as a function of fibre orientation and the magnitude of the applied external force, as the basis of an all-fibre sensor system. In addition, the force/pressure sensitivities of different pairs of these PCFs when they were fusion-spliced together were evaluated and cross-compared. To obtain an optimum output from these systems, a polarization controller is used in a fibre loop mirror configuration to ensure that a fusion-spliced pair of PCFs is created having the same birefringence angle. The results obtained show that PCFs of low birefringence (Low-Bi) are more sensitive than those of high birefringence (Hi-Bi), although the former require a greater length to achieve a similar effect due to the birefringence. Compared to conventional, non-PCF Hi-Bi fibres (e.g. Panda and Bow-Tie fibres), PCFs demonstrate a much lower temperature sensitivity, allowing them to be well suited to measuring force, pressure and mass in real time (when the temperature is varying) by using a fibre loop mirror (FLM) configuration. In addition, the results obtained show that the sensitivity of the fusion-spliced fibre pairs is lower than that of a single PCF with low and medium birefringence, but more sensitive than that of a single PCF with high birefringence. [Copyright &y& Elsevier]

The liquid crystalline filter exhibiting particular optical properties is presented. Their basis application is the multiresolution image analyzer based on a wavelet transform (WT). In co-operation with the phase shifter such a filter allows to rotate the polarization of the transmitted light. The resulted intensity distribution has been exploited as a tool to span the transmitted image onto the space of the circular Haar wavelets. It provides new possibilities in an optical signal processing. The analysis of the light transmission in considered filter as well as the wavelet space creation are also described. [ABSTRACT FROM AUTHOR]

Digging two vertical shafts with the multiple blasts technique gave the opportunity to measure the induced angular motions in a horizontal plane with well-defined positions of sources. Three kinds of rotation rate sensors, sharing an underground location, were used. Two of them—a Fiber-Optic System for Rotational Events & phenomena Monitoring (FOSREM) and a prototypical seismometer housing the liquid-filled torus—sensed the rotation, while a microarray of two double-pendulum seismometers sensed both the rotation and symmetric strain. The FOSREM was sampled at 656.168 Hz, while all the others were only sampled at 100 Hz. There were considerable differences within the results gathered from the mining blasts, which should be attributed to two causes. The first one is the difference in principles of the operation and sampling rates of the devices used, while the other is the complex and spatially variable character of the studied wave fields. Additionally, we established that the liquid-filled sensor, due to its relatively low sensitivity, proved to be viable only during a registration of strong ground motions. Overall, a comparative study of three different rotational seismometers was performed during mining-induced strong ground motions with well-localized sources. [ABSTRACT FROM AUTHOR]

A polymer microtip manufactured at the end of a multi-mode optical fiber by using the photopolymerization process offers good reflective properties, therefore, it is applicable as an optical fiber sensor micro-transducer. The reflective properties of this microelement depend on the monomer mixture used, optical fiber type, and light source initiating polymerization. Experimental results have shown that a proper selection of these parameters has allowed the design of a new class of sensing structure which is sensitive to the refractive index (RI) changes of a liquid medium surrounding the microtip. An optical backscatter reflectometer was applied to test a group of micro-transducers. They were manufactured from two monomer mixtures on three different types of multi-mode optical fibers. They were polymerized by means of three optical light sources. Selected micro-transducers with optimal geometries were immersed in reference liquids with a known RI within the range of 1.3–1.7. For a few sensors, the linear dependences of return loss and RI have been found. The highest sensitivity was of around 208 dB/RIU with dynamic 32 dB within the range of 1.35–1.48. Sensing characteristics have minima close to RI of a polymer microelement, therefore, changing its RI can give the possibility to tune sensing properties of this type of sensor. [ABSTRACT FROM AUTHOR]

This paper presents the influence of a thin metal layer deposition on the surface of a tapered optical fiber surrounded by a low liquid crystal, on light propagation inside the taper structure. In this research, three types of liquid crystal cells were under investigation: orthogonal, parallel, and twist. They differed by the rubbing direction of the electrodes in relation to the fiber axis determining the initial molecule arrangement inside the cell. Gold films with thickness d = 30 nm were deposited on the tapered fiber surface in the tapered waist area. Cells including a tapered optical fiber with no metallic layer were also examined and presented as a reference. All measurements were performed at room temperature for a different steering voltage U from 0 to 200 V, with and without any amplitude modulation with a frequency f = 5 Hz, and the wavelength λ range from 550 to 1200 nm. As a result, the resonant peaks were obtained, which depends on a liquid crystal cell type and steering voltage, as well. This paper shows the possibility of sensing the change of applied voltage by the constructed system. During measurements, additional effects as signal overlapping and intermodal interference were observed reducing measured voltage value. In the future, the improved, similar systems that will have a better response could be used as a sensor of factors to which liquid crystal (LC) will be sensitive, especially temperature and electric field. [ABSTRACT FROM AUTHOR]

• In this work, we study a ferroelectric liquid crystal (FLC) cell as a phase-only modulator. The novelty of the approach is the use of a FLC cell with a large switching rotation angle close to 90° instead of the typical value used in display applications, which is less than 45 ∘. • We show that when the LC layer is a half-wave retarder, this device provides a binary π phase modulation for any input state of polarization and with maximum light conversion efficiency, thus being useful even for unpolarized light. This situation is not possible with the common nematic LC modulators or with standard FLC modulators of smaller rotation angles. • The main physico-chemical properties of the liquid crystalline mixture used to fabricate the FLC modulator are studied. In addition, we perform a reverse engineering procedure aimed at verifying the modulator's physical parameters and the binary π -phase modulation. In this work a ferroelectric liquid crystal (FLC) modulator with a non-standard large switching rotation angle, close to 90 ∘ , is fabricated and characterized. The modulator acts as a switchable wave-plate with an in-plane rotation of the principal axis under the action of a bipolar voltage. In the ideal situation of half-wave retardance, the device is shown to behave as a binary π phase modulator independently of the input state of polarization. We provide physico-chemical properties of the liquid crystalline mixture used to fabricate the FLC modulator with such large switching angle. The characterization method of the device optical properties is presented, which allows the localization of the two LC stable states, the unambiguous determination of the rotation angle, and the evaluation of the spectral retardance function. We demonstrate the polarization-independent π phase shift using an adapted Young's type interferometer for real-time measurements, where we further analyze the operational frequency limits of the device. This FLC operational mode can be exploited to produce binary-phase polarization-independent diffractive optical elements. [ABSTRACT FROM AUTHOR]

Polymer microtips are 3D microstructures manufactured on the end face of an optical fiber by using the photopolymerization process. Such micro-optic elements made on a multi-mode optical fiber were previously tested as a transducer of refractive index sensor. These studies were an inspiration to investigate the possibility of using this type of transducer to measure the presence of volatile organic compounds in the air. The experimental results of microtips polymerized with UV and VIS were reported. It was possible to detect the presence of five different volatile compounds in the air due to the sensitivity of the transducer to the refractive indices changes. These changes were induced by the vapors condensed on the microtip surface. The measured time responses have shown that the return loss decreases rapidly as the microtip is inserted inside a glass vial filled with the tested compound. Moreover, correlations between calculated dynamic ranges and refractive indices and volumes of the volatile compounds inside the vials were negligible. Therefore, this type of sensor can be categorized as a condensed material threshold sensor. This sensor can be used in warning systems for monitoring leakages of pipelines carrying volatile chemicals. [ABSTRACT FROM AUTHOR]

This paper is a continuation of previous work and shows the enhancement of the surface plasmon resonance effect in a tapered optical fiber device. The study investigated liquid crystal cells containing a tapered optical fiber covered with a silver nanolayer, surrounded by a low refractive index liquid crystal in terms of the properties of light propagation in the taper structure. Silver films with a thickness of d = 10 nm were deposited on the tapered waist area. Measurements were performed at room temperature; liquid crystal steering voltage U from 0 to 200 V, with and without any amplitude modulation with a frequency of f = 5 Hz, and the wavelength λ ranged from 550 to 1200 nm. A significant influence of the initial arrangement of liquid crystals molecules on light propagation was observed. Three types of liquid crystal cells—orthogonal, parallel, and twist—were considered. During the measurements, resonant peaks were obtained—the position of which can also be controlled by the type of liquid crystal cells and the steering voltage. Based on the obtained results, the best parameters, such as highest peak's width reduction, and the highest SNR value were received for twisted cells. In addition, the present work was compared with the previous work and showed the possibility of improving properties of the manufactured probes, and consequently, the surface plasmon resonance effect. In the presented paper, the novelty is mainly focused on the used materials as well as suitable changes in applied technological parameters. In contrast to gold, silver is characterized by different optic and dielectric properties, e.g., refractive index, extension coefficient, and permittivity, which results in changes in the light propagation and the SPR wavelengths. [ABSTRACT FROM AUTHOR]

A homologous series of new ferro- and antiferroelectric liquid crystals, containing 2′,3′-difluorosubstituted terphenyl core as a mesogenic core, has been recently synthesised. Synthetic routes and mesomorphic properties were described. Liquid crystal phases were preliminarily determined by thermomicroscopic and microcalorimetric measurements and verified by dielectric measurements and miscibility methods. Temperatures and enthalpies of phase transitions are given. [ABSTRACT FROM AUTHOR]

A bicomponent mixture in the orthoconic aniferroelectric phase, based on three-ring esters with fluorine atoms and ether group in a nonchiral chain, was doped with a variety of cyano-terminated compounds containing different numbers of phenyl rings in a rigid core and a terminal chain of different chirality. Compounds with two chiral chains were added to the basic mixture. The influence of the structure and concentration of dopant on the temperature-dependence of helical parameters, such as helical pitch and twist sense, were assessed by spectrophotometric and polarimetric methods. Long cyano-terminated compounds were found to be better than the other dopants tested for improving the usable properties of the antiferroelectric mixtures. [ABSTRACT FROM AUTHOR]

We have performed nonlinear optical and piezoelectric studies of the Rb1-xKxTiOPO4 (RKTP) (with x = 0.01 and 0.002) single crystals irradiated by γ-quanta at power 1.23 Gy. We have found that for non-irradiated samples with x = 0.01 the effective second-order susceptibilities determined from the powder-like micrometer samples were less than for x = 0.02 and the effective values of the second-order susceptibilities for 1064 nm were equal to 3.12 pm/V (x = 0.002) and 2.56 pm/V (x = 0.01). After the gamma irradiation the corresponding values were equal to 2.45 pm/V and 2.78 pm/V, respectively. Moreover, for the samples with x = 0.01 one can observe the occurrence of the damage at laser energy density equal to about several J/cm2. Such effect is absent for the pure KTP crystals and may be a consequence of substantial role of the intrinsic defects caused by insertion of potassium ions in the positions of the rubidium cations. At the same time the piezoelectrical constants show an opposite behavior with respect to the SHG. [ABSTRACT FROM AUTHOR]

Liquid crystal materials composed of mixed nematic compounds find broad use in liquid crystal displays and photonic applications. A ternary mixture formed from three different nematic compounds shows peculiar behavior such as tunable electro-optical properties dependent on the frequency of the driving voltage. The paper presents an analysis of the response time and phase retardation of a frequency tunable nematic liquid crystal mixture (under code name 5005). This material possesses high birefringence (Δn = 0.32 at 633 nm) as well as high dielectric anisotropy (Δε = 6.3 at 100 Hz). The unique property of the 5005 mixture is frequency-controlled phase modulation, as in a dual frequency liquid crystal, while dielectric anisotropy goes to zero instead of being negative at high frequencies. For each component of the mixture, details on mesomorphic properties and their role in the formulation of the mixture are reported. The 5005 mixture was characterized by multiple investigation techniques, such as temperature dependence dielectric anisotropy, transmittance measurements image polarizing microscopy, and UV stability. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by modification of a TOF cladding by the alkanes used, characterized by phase change. Temperature changes cause power transmission changes creating a switcher or a sensor working in an ON-OFF mode. Phase change temperatures and changes in the refractive index of the alkane used directly affected power switching. Alkanes were doped with ZnS:Mn NPs to change the hysteresis observed between ON-OFF modes in pure alkanes. The addition of nanoparticles (NPs) reduces the difference between phase changes due to improved thermal conductivity and introduces extra nucleating agents. Results are presented in the wide optical range of 550–1200 nm. In this investigation, hexadecane and heptadecane were a new cladding for TOF. The higher alkanes were doped with ZnS: Mn NPs in an alkane volume of 1 wt.% and 5 wt.%. The thermo-optic effect can be applied to manufacture a thermo-optic switcher or a temperature threshold sensor. [ABSTRACT FROM AUTHOR]

In searching for new functional self-assembling materials a multicomponent ferroelectric liquid crystalline mixtures with features appropriate for utilization in photonic and electro-optic devices have been designed. Designed mixtures are composed of bicyclic pyrimidine achiral compounds and chiral dopants with an oligophenyl rigid core and two homochiral terminal chains. Basic mesomorphic, electro-optical and structural properties have been carefully studied and discussed. For several mixtures stable enantiotropic ferroelectric phase with very good alignment and desired functional features in surface stabilized geometry have been found. Based on these properties and computational as well as conformational analysis of chiral dopants, the structure-property relations have been established and analysed. Unlabelled Image • Mixtures of olighophenyl chiral dopants and achiral mixture have been designed. • The structure–property correlations for designed mixtures have been established. • Desired tilt angle, low viscosity and spontaneous polarization are observed. • Good electro-optical performance of SSFLC structure are achieved. • The designed mixtures can be used for functional optoelectronic and photonic devices. [ABSTRACT FROM AUTHOR]

Polymeric materials are widely used because of their variety and modification ability. Multifunctional acrylates deserve special attention due to their feasibility of photopolymer development. We reported a new class of polymers produced by photopolymerization using VIS and UV radiation. Monomer mixtures consist of monomers, photo-initiators and co-initiators for VIS or monomers and photo-initiators for UV photopolymerization. One selected monomer was used in each mixture i.e. DTMPTA—trimethylolpropane tetraacrylate, TMPTA—trimethylolpropane triacrylate or TCDMA—tricyclodecanedimethanol diacrylate. Silicone oil terminated by hydroxyl groups—(OH–TSO) was used as the adjuvant sorption material. To characterise the physicochemical properties of obtained materials, instrumental analysis methods were applied. By using chromatographic analysis, it was shown experimentally that the new photopolymer materials have a high sorptive capacity and increased sorption selectivity towards selected organosulfur and organophosphorus compounds. This could result in the use of these new materials as sorption fibers used during solid-phase microextraction (SPME). Image 1 • Multifunctional acrylic monomers were used to produce new sorption materials. • Photopolymerization with light of different wavelengths was used. • Two different light sources were used during the polymerization. • Polymers have great sorption properties in relation to selected CWAs simulants. • These developed photopolymers could be used as SPME fiber coatings. [ABSTRACT FROM AUTHOR]

The technology of polymer microtips' manufacturing on the ends of selected multi-mode fibers has been reported. The study's key element was an extended description of technology parameters' influence on the shape of these 3D microstructures. Basic technology parameters such as spectral characteristics of the light source, monomer mixture type, optical power, and exposure time were taken under consideration. Depending on those parameters, different shapes, sizes, and surface structures of microtips were obtained. The spectral characteristics of the light and optical power delivered to a monomer drop were identified as the most important parameters for the formation of the desired 3D shape of the microtip. Presented experimental results are the base for further studies directed to the application of these micro-elements in the fields of optical measurements and sensors' technology. [ABSTRACT FROM AUTHOR]

In this work, we report the experimental results on optimizing the optical structure for ambient refractive index measuring with temperature changes monitoring. The presented optical structure is based on a dual-resonance long-period grating embedded inside a fiber loop mirror, where the long-period grating acts as the head of the refractive-index sensor, whereas the section of polarization maintaining fiber in the loop mirror ensures suitable temperature sensing. The optimization process was comprised of tuning the resonance and interferometric peaks by changing the state of polarization of propagating beams. Experimental results establish that the response of the proposed sensor structure is linear and goes in opposite directions: an increase in the ambient refractive index reduces the signal response, whereas a temperature increase produces an increased response. This enables us to distinguish between the signals from changes in the refractive index and temperature. Due to the filtering properties of the interferometric structure, it is possible to monitor variation in these physical parameters by observing optical power changes instead of wavelength shifts. Hence, the refractive index sensitivity has been established up to 2375.8 dB/RIU in the narrow RI range (1.333–1.341 RIU) and temperature sensitivities up to 1.1 dBm/°C in the range of 23–41 °C. The proposed sensor is dedicated to advanced chemical and biological sensor applications. [ABSTRACT FROM AUTHOR]