An angle sensor based on polymer optical fibers with cladding doped by rhodamine B

Polymer or plastic optical fibers' performance lies somewhere between conventional copper wires and glass optical fibers. Copper wires suffer from electromagnetic interference. By comparison, plastic optical fibers are free from interference. Compared to glass fibers, polymer optical fibers (POFs) are much easier to connect because of their large diameters. Coupling of light from the sun or from a source is also very efficient due to large NA and large core diameter. The most important attribute of POFs is their large core diameters of around 1 mm to 20 mm as compared to glass fibers with cores of 50/spl mu/m or 62.5/spl mu/m. Such a large diameter results in easier alignment at joints. Any transverse misalignment between the two cores across a joint between two fibers leads to a loss. Hence, this paper studies on the coupling efficiency of light from the sun as a natural light source to a step-index polymer optical fibers in comparison to glass fibers that results in larger light-gathering power for optical fiber daylighting system and in fiber decorative lighting. MATLAB simulation analysis shows that the coupling efficiency and light gathering power increases steadily with an increase in numerical aperture of the step-index PMMA polymer optical fiber that has higher and better light gathering power than step-index PMMA glass optical fiber.

Polymer optical fibers (POFs) have significant advantages over numerous sensing applications. The key element in developing sensor is by removing the cladding of the fiber. The use of organic solvent is one of the methods to create tapered POF in order to expose the core region. In this study, the etching chemicals involved is acetone, methyl isobutyl ketone (MIBK), and acetone-methanol mixture. The POF is immersed in 100%, 80%, and 50% of acetone and MIBK dilution. In addition, the mixture of acetone and methanol is also used for POF etching by the ratio 2:1 of the volume. Acetone has shown to be the most reactive solvent towards POF due to its fastest etching rate compared to MIBK and acetone-methanol mixture. The POF is immersed and lifted from the solution for a specific time, depending on the power loss properties for the purpose of producing unclad POF. In comparison to silica fiber optic, the advantages of POF in terms of its simple technique and easy handling enable it to produce unclad POF without damaging the core region. The surface roughness of the POF is investigated under the microscope after being immersed into different solvent. This method of chemical tapering of POF can be used as the fundamental technique for sensor development. Next, the unclad fiber is immersed into ethanol solutions in order to determine the reaction of unclad POF towards its surrounding. The findings show that this particular sensor is sensitive towards concentration changes ranging between 10 wt% to 50 wt%.

In this paper, we present a study aimed at characterizing the optimal fiber optic components for Brillouin sensing in multimode fibers. For this purpose the use of single-mode and multimode circulators as well as couplers typically used in the Brillouin measurement setups was investigated. On the one hand the undesired coupling losses between conventional fiber optic measurement system components and a multimode sensor fiber can be overcome by replacing the singlemode components with their own multimode equivalents. On the other hand the use of multimode fiber optic circulators and multimode couplers affects the mode distribution of laser light which can impair the measurement signal backscattered in the multimode sensor fibers. In view of an increasing interest in high strain measurements using polymer optical fibers (POFs) as Brillouin-distributed sensors the investigation on Brillouin scattering effects in multimode fibers (MMFs) was performed on a low-loss perfluorinated graded-index polymer optical fiber (PFGI-POF). The obtained results were compared with those of a standard graded-index multimode (GI-MMF) silica glass optical fiber (GOF). This study confirms the relevance of the adaptation of the measurement system components to the use of the multimode sensor fibers. In addition, due to mode coupling effects occurring in the tested POF itself, the results show differences in the yield of the components adaptation in the sensory implementation of the two kinds of the tested optical fibers.

The automotive industry is a promising area for innovations in the field of polymer optical fiber (POF) sensors as the industry currently uses the POF mostly for data transmissions. Since an optical fiber sensor has a high bandwidth, is small in size, is lightweight, and is immune to electromagnetic interference, it offers higher performance than that of its electrical-based counterparts such as the strain gage, elastomeric bladder, and resistive sensor systems. This enhanced performance makes an optical fiber sensor a suitable material for sensing seat occupancy for improved safety features in automobiles. The overall goal of this research is to develop a textile-based optical fiber sensor for automotive seat occupancy with high accuracy and reproducibility. In this study, the bending and tensile loading responses of POF were investigated, where two perfluorinated (PF) graded index (GI) POFs with two different core/cladding diameters, 62.5/750 and 62.5/490 μm, were used. The bending loss and the light attenuation against the applied axial stress were measured by a photon counting optical time-domain reflectometer. The critical bending diameters were analyzed: Cytop-1 (62.5/750 μm) ≥ 38.10 mm, Cytop-2 (62.5/490 μm) ≥ 44.45 mm. Furthermore, the elastic sensitive strain regions (x), where the stress-induced loss was recoverable, of the POFs at a 76.2 mm gage length at a strain rate of 4 mm/min were determined: Cytop-1: 3% ≤ x ≤ 3.5%, Cytop-2: 3.1% ≤ x ≤ 3.3%. The Cytop-1 was found to be less sensitive to bending and to have greater elastic sensitive strain range relative to the Cytop-2. In this study, a theoretical approach of the PF GI POF behavior to bending and axial tension was provided. The results demonstrated the feasibility of POFs as optical fiber sensors for automotive seat occupancy sensing.

Fiber optic sensors based on polymer optical fibers (POF) take advantage of the high elasticity and high break-down strain of POF. Because of their outstanding elastic properties, POF are well suited for integration into technical textiles like geotextiles and medical textiles. Smart textiles with incorporated POF sensors, able to sense various mechanical and physical quantities, can be realized. The integration of POF as a sensor into geotextiles for monitoring of displacement of soil is very attractive since POF can be used for distributed strain measurement of strain values of more than 40 %. An online monitoring of critical mechanical deformations of geotechnical structures like dikes, dams, slopes, embankments as well as of masonry structures can be ensured. Medical textiles that incorporate POF sensors can control vital physiological parameters like respiratory movement and can be used for wearable health monitoring of patients requiring a continuous medical assistance and treatment. The biocompatibility of POF is an important criterion for selecting POF as a medical sensor. The paper shows selected examples of using POF sensors for the mentioned monitoring purposes.

This paper presents an analysis of the mechanical properties of different polymer optical fibers (POFs) at ultraviolet (UV) radiation conditions. Cyclic transparent optical polymer (CYTOP) and polymethyl methacrylate (PMMA) optical fibers are used in these analyses. In this case, the fiber samples are irradiated at the same wavelength, pulse time and energy conditions for different times, namely, 10 s, 1 min, 2 min and 3 min. The samples are tested in tensile tests and dynamic mechanical thermal analysis (DMTA) to infer the variation in the static and dynamic properties of such fibers as a function of the UV radiation condition. Furthermore, reference samples of each fiber (without UV radiation) are tested for comparison purposes. The results show a lower UV resistance of PMMA fibers, i.e., higher variation in the material features in static conditions (Young’s modulus variation of 0.65 GPa). In addition, CYTOP fiber (material known for its high UV resistance related to its optical properties) also presented Young’s modulus variation of around 0.38 GPa. The reason for this reduction in the moduli is related to possible localized annealing due to thermal effects when the fibers are subjected to UV radiation. The dynamic results also indicated a higher variation in the PMMA fibers storage modulus, which is around 30% higher than the variations in the CYTOP fibers when different radiation conditions are analyzed. However, CYTOP fibers show a smaller operational temperature range and higher variation in the storage modulus as a function of the temperature when compared with PMMA fibers. In contrast, PMMA fibers show higher variations in their material properties when subjected to oscillatory loads at different frequency conditions. Thus, the results obtained in this work can be used as guidelines for the influence of UV radiation in POFs not only for the material choice, but also on the limitations of UV radiation in the fabrication of the grating as well as in sensor applications at UV radiation conditions.

In this thesis we focus on the integration of optical fibres in textiles to create wearable sensing systems. In the introduction (Chapter 3) we describe the basics of light guiding in optical fibres and methods of lateral light coupling. Subsequently, a literature review and motivation are presented. Afterwards two main parts can be differentiated. In the first one (Chapters 4, 5) a new method of continuous extrusion of optical fibres and their medical sensing application using photoplethysmography (PPG) is described. In the second part (Chapters 6 and 7) we present an optical fibre based force sensor, and demonstrate its application in respiratory monitoring. Commercially available optical fibres are not suitable for integration into textiles for two main reasons. These are: low flexibility in bending the fiber and relatively high price. Thus, a new type of Polymeric Optical Fibres (POFs) was developed in Empa St. Gallen. These fibres have enhanced strength and flexibility (0.027 GPa for in-house produced POF vs 2.6-3.5 GPa for commercial POF). additionally, these optical fibres where produced by means of melt spinning, which increased significantly the production speed (400 m/min) and thus otentially reduce the price of these POFs. Cyclo-olefin polymer (COP) (Zeonor n=1.5) was used as a core material and THV fluoropolymer (THVP, n=1.35) as a cladding. These produced POFs features propagation loss at the level of 9 dB/m at 652 nm. These optical fibres were embroidered into textiles such that out-coupling and in-coupling of light at narrow bends in the fiber was possible and the efficiency was improved by one order of magnitude (0.07 % vs formerly achieved 0.008 %). These flexible POFs served to manufacture a textile-based PPG monitoring system. The sample featuring the best coupling efficiency was used to measure heart rate and oxygen saturation (SpO2). Obtained results were compared with a hospital standard device and showed very good correlation. Moreover, the system was adapted to work in reflection mode which makes the sensor more versatile. In the second part of the thesis we present a new type of polymeric optical fibre for applications in force sensing systems in textile fabrics. The detectable force ranges from 0.05 N to 40 N (applied on 3 cm of fibre length) and can be adjusted beyond these limits. The fibres have attenuation parameters between 0.16 - 0.25 dB/cm at 652 nm and the yield strength ranging from 3.9 to 5.4 MPa. Additionally, these optical fibres where employed to develop a textile-based respiratory sensing system. Fibres with different sensitivity together with different setups were evaluated. The results obtained from the textiles based system were compared with commercial standards and showed good correlation. Furthermore, we showed that such a wearable system is able to differentiate the type of breathing (diaphragmatic, upper costal and mixed) when the sensor is placed at different torso positions. Overall, we demonstrated that the new types of POFs exhibit great potential in the sensing textile applications. Moreover, the proposed production technique of POFs is fast, and thus the price of the POFs can be lowered, and therefore accepted by the textile industry.

PurposeThis paper aims to investigate how different knitted structures affect the illuminative effect of polymeric optical fibres (POFs).Design/methodology/approachKnit prototypes were constructed using a 7-gauge industrial hand flat knitting machine. The textile prototype swatches developed in this study tested POF illumination in three types of knitting structures: intervallic knit and float stitch structures; POF inlaid into double plain and full cardigan structures; and double plain and partial knitting structures. The illuminative effects of the POFs in seven prototype swatches were analysed and compared.FindingsIt is possible to use an industrial hand flat knitting machine to knit POFs. Longer floats expose more POFs, which boosts illumination but limits the textile’s horizontal stretchability. The openness of the full cardigan structure maximises POF exposure and contributes to even illumination. The partial knitting in different sections achieves the most complete physical integration of POFs into the knitted textiles but constrains the horizontal stretchability of the textiles.Practical implicationsThe integration of POFs into knitted textiles provides a functional illuminative effect. Applications include but are not limited to fashion, architecture and interior design.Originality/valueThis study is novel, as it investigates new POF knitted textiles with different loop structures. This study examines how knit stitches affect POFs in intervallic knit and float stitch, inlaid POF double knit, double plain and partial knit and the illuminative effects of the knitted textile.

Polymer optical fibers (POF) have received increased attention in recent years in the fields of data communication and sensing applications. The lower cost and higher flexibility are the main advantages of POF compared to silica fibers and make them interesting candidates for Fiber Bragg grating (FBG) sensor applications. FBG are convenient measurement devices for strain and temperature measurements, as they can be multiplexed within one fiber yielding a sensor array and the fiber can be embedded in structures. This work investigated the possibility of producing FBG in polymer fibers and their use as sensor units. It could be shown that using excimer laser irradiation at 308 nm, it is possible to write FBG in single-mode POF employing a standard phase mask, side writing technique. Index changes of up to 1.7 × 10-4 and reflectivies of up to 87% could be reached. The induced refractive index change due to pulsed UV irradiation was shown to be negative. The polymer material of the core (Polystyrene (PS) / Polymethyl methacrylate (PMMA)) was not sensitized prior to irradiation. During the grating formation an irradiation induced insertion loss of up to 11 dB/cm was observed. Excimer laser written FBG showed stability of over 9 months for approximately 40% of written FBG. Results of FBG writing using femto second laser irradiation showed FBG with reflectivities of up to 1.2 × 10-4, however these POFBG were not stable. The POFBG were characterized using optical low coherence reflectometry (OLCR) which enables to calculate the FBG location and length as well as the induced amplitude Δnac and mean refractive index change Δndc. Taking into account fiber and insertion losses, good agreement of these calculations and measurements were found. The results show that large variations of the induced index change result from irradiation. Local index change peaks of up to 4 times the mean value were observed, indicating inhomogeneity of the fiber material. Birefringence in the core of the POF (≈ 1.2 × 10-3) is up to a factor 3 higher than in the cladding which is due to the PS content within the core. The birefringence is due to inelastic strain and stress induced in the drawing process. Annealing, uniform irradiation and FBG writing using 308 nm excimer laser light induces a decrease of the absolute birefringence value. The changes upon irradiation are confined to the core of the fiber. Large variations in the initial and final birefringence before and after irradiation support the findings of the OLCR measurements indicating material inhomogeneities in the fiber. POFBG were found to be sensitive to relative humidity, temperature and strain. This is in contrast to glass fiber FBG which do not show humidity sensitivity. POFBG relative humidity sensitivity is non-linear with a change of up to 8 nm for a RH change of ≈ 100%. The non-linearity is introduced by a non-linear water sorption process. The POF grating response to temperature changes under dry conditions (1.5±1 % RH) is –10±0.5 pm/°C. The temperature response of the FBG submerged in water is –36±2 pm/°C due to an increased thermal expansion coefficient and a change in polarizability. Under ambient conditions the grating response to heating is typically ≈ –138 pm/°C, predominantly due to a change in POF swelling, i.e changes in relative humidity and POF water content. The diffusion coefficient of water in this POF at 23.5°C is 6.7 × 10-9cm2/s for sorption and 10 × 10-9cm2/s for desorption. Equilibrium of water content within the fiber and the surrounding air is typically reached after approximately one hour. Calculation showed that a reduction of the fiber diameter can increase this humidity sensitivity response time down to approximately 5 minutes for a fiber diameter of 25 µm.

Problem statement: Polymer Optical Fiber (POF) has many advantages making it the choice of today's communication, especially in auto motive industry. This communication requires low cost ways for much information to be sent simultane ously. Because of this, using Wavelength Division Multiplexing (WDM) concept, a low cost and green 3 ×3 POF splitter is fabricated. It is fabricated using cheap and easy-to-find tools such as metal tu be and candle. Approach: The fabrication is being done by taking three strands of POF and heating the middle parts so that it will melted and fused together until it elongated and shrink to a diamete r of 1 mm. Successfully fabricated POF splitter are characterized by measuring the output losses, befor e and after the POF's end is being smoothed and polished using two sand study of different degree o f coarseness. This is to observe the effect of polishing on optical signal losses. POF splitter's losses are also measured on different temperature t o observe the effect of temperature on the splitter's performance. Results: Based on the result, it is obvious that cleanliness and a flat POF's end surfa ce influenced the losses with a reduction between 0.3- 5.0 dB. Temperature, even though subtle, does also affect the signal losses with increased losses averaging around 0.3 dB. Overall, the losses in the fabricated POF splitter are still high, but show promising improvement with amelioration of fusion technique and the use of tools with higher quality. Conclusion: This low cost fabrication technique is believed to commercially produce cheap POF splitter, but with more in-depth research on the fu sion technique, source of losses and ways to minimize the losses and improve output optic signal s.

We propose to implement a modularly structured planar wave-guiding star-coupler for large-corepolymer fiber-based optical interconnect applications. An 8x8 version of the coupler is demonstrated using polymer materials. The planar star-coupler can be mass-produced using injection molding technology at substantially low cost. Measurements indicate that by properly working out a trade-offbetween device compactness, uniformity and coupling efficiency, a < 2.0 dB power fluctuation among all receiving channels and a 3. 1 dB excess power loss are obtainable. I. Introduction Recent surge of interest in polymer optical fibers (POFs) was powered by the belief that large core POF's may oneday become a cost-effective sub-local interconnect solution for many data communication applications [1]. It has beendemonstrated that material, production, as well as connection costs of POF's are appreciably lower than those of glassfibers. It is further believed that once POF's are widely accepted, their costs could become compatible to the costs of coppertransmission lines of inferior bandwidth. While research on finding low-loss POF materials and low-cost productionmethods is actively being pursued [2-3], attention has also been paid to low-cost connection schemes. Large core size, andhigh material flexibility provide many opportunities to decrease coupling and connection costs for POF's. Etched-mirror-based side-couplings have been used to couple light in and out of POF cost-effectively [4-5]. In the current work, wepropose a low-cost POF star-coupling structure which can be assembled in an un-controlled environment. In addition, theusage of this plug-and-play fiber optic component requires minimum training.A star-coupler is an important passive fiber optic component because it allows multiple signal broadcasts. A starcoupler can then be widely used in both time-division or wavelength-division based networks, such as optical buses [6-8].One way of fabricating a star-coupler uses a planar geometry where a one-dimensional (1D) flat cavity is sandwichedbetween an input and an output linear arrays of waveguides [9-1 1]. Such planar star-couplers for single-mode and multimodeglass fibers are now commercially available. Beside the high fabrication cost of such couplers, users need to pay anadditional cost of interfacing such couplers with conventional fibers. In the following section, we devise a planar POF star-coupler which uses cost-effective injection-molding fabrication technology, and requires no additional fiber interfacing cost.

The aim of the study was to verify the usefulness of commercially available granulates of PMMA (poly (methyl methacrylate) and PS (polystyrene) for the production of polymer optical fibers by extrusion method. Samples were subjected to thermal processing in various conditions (different temperatures and exposure time). Thermal (TG/DTG) and spectroscopic (ATR/FT-IR) analyses were carried out to analyze changes in the samples. Based on FT-IR analysis of liquid monomers and granulates the conversion of double bonds was calculated, which gave us a picture of the degree of monomers conversion, crucial information from the technological point of view. Full Text: PDF ReferencesO. Ziemann, J. Krauser, P.E. Zamzow, W. Daum, POF Polymer Optical Fibersfor Data Communication (Berlin: Springer 2008). DirectLink P. Stajanca et al. "Solution-mediated cladding doping of commercial polymer optical fibers", Opt. Fiber Technol. 41, 227-234, (2018). CrossRef K. Peters, "Polymer optical fiber sensors—a review", Smart Mater. Struct., 20 013002 (2011) CrossRef J. Zubia and J. Arrue, "Plastic Optical Fibers: An Introduction to Their Technological Processes and Applications", Opt. Fiber Technol. 7 ,101-40 (2001) CrossRef M. Beckers, T. Schlüter, T. Gries, G. Seide, C.-A. Bunge, "6 - Fabrication techniques for polymer optical fibres", Polymer Optical Fibres, 187-199 (2017) CrossRef M. Niedźwiedź , M. Gil, M. Gargol , W. Podkościelny, P. Mergo, "Determination of the optimal extrusion temperature of the PMMA optical fibers", Phot. Lett. Poland 11, 7-9 (2019) CrossRef

Polymer optical fibers (POFs) have significant advantages for many sensing applications,including high elastic strain limits, high fracture toughness, high flexibility in bending, highsensitivity to strain and potential negative thermo-optic coefficients. The recent emergenceof single-mode POFs has enabled high precision, large deformation optical fiber sensors.This article describes recent advances in both multi-mode and single-mode POFbased strain and temperature sensors. The mechanical and optical propertiesof POFs relevant to strain and temperature applications are first summarized.POFs considered include multi-mode POFs, solid core single-mode POFs andmicrostructured single-mode POFs. Practical methods for applying POF sensors, includingconnecting and embedding sensors in structural materials, are also described. Recentdemonstrations of multi-mode POF sensors in structural applications based on newinterrogation methods, including backscattering and time-of-flight measurements, areoutlined. The phase–displacement relation of a single-mode POF undergoing largedeformation is presented to build a fundamental understanding of the response ofsingle-mode POF sensors. Finally, this article highlights recent single-mode POFbased sensors based on polymer fiber Bragg gratings and microstructured POFs.

Polymeric optical fibers (POF) presents some advantages compared to the glass optical fibers as flexibility, higher numerical aperture (NA), ease in handling and connecting due to their larger diameter and lower cost manufacturing and installation.However, due to their larger transmission losses compared to the main applications of glass fibers, POF are limited to short distances, such as local area networks (LAN), vehicle electronics, industrial automation, sensors, guides lighting and displays.PMMA -poly (methyl methacrylate) is the most common material used in the core of optical devices, since it has better optical properties in comparison with other optical polymers such as PS (polysterene) and PC (polycarbonate).In this study, it is proposed a new method to manufacture POF by vertical extrusion using PMMA and PVDFpoly (vinylidene fluoride) as core and cladding materials, respectively.The polymers are simultaneously extruded using the same die, taking advantage of their compatibility and similar processing parameters.The POF produced were characterized for core and cladding morphology and composition, by optical microscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX or EDS) and optical properties measurements of loss attenuation as a function of wavelength.The lowest spectral attenuation measured of the produced POF was 10,70 dB/m at 840 nm.Likely, lower losses could be expected if a more appropriated cleaving method for POF would be used and improvements on fiber coupling for loss attenuation measurements.In addition, the losses measured are also due to the irregular thickness of the fluorinated layer (cladding) around the core of the POF produced.Although, improvements are needed to get a FOP with regular diameters of cores and cladding, the one-step process developed for POF manufacturing by simultaneous extrusion of PMMA (core) and PVDF (cladding) showed to be feasible and could be a potential process for ease production of POF for short length applications.

Polymer optical fiber and fiber Bragg grating sensors for biomedical engineering Applications: A comprehensive review