Plastic optical fiber

This Letter presents simulation and experimental results that explore bending insensitivity of fiber Bragg gratings in suspended-core optical fibers. The implementation of thin silica bridge in the fibers enhances index contrast of the fiber core and reduces bending-induced strain transfer to the fiber core. This fiber design lead to a reduction of over 7 times in strain-induced fiber Bragg grating resonant peak shifts in the suspended-core fiber compared with that in standard telecommunication fiber, and an 0:14 dB bending loss at a bending radius of 6:35 mm.

This Letter presents simulation and experimental results that explore bending insensitivity of fiber Bragg gratings in suspended-core optical fibers. The implementation of thin silica bridge in the fibers enhances index contrast of the fiber core and reduces bending-induced strain transfer to the fiber core. This fiber design lead to a reduction of over 7 times in strain-induced fiber Bragg grating resonant peak shifts in the suspended-core fiber compared with that in standard telecommunication fiber, and an 0:14 dB bending loss at a bending radius of 6:35 mm.

Concrete is a composite material composed of coarse granular material (the aggregate or filler) embedded in a hard matrix of material (the cement or binder) that fills the space among the aggregate particles and glues them together. Translucent concrete is a concrete based building material with light-transmitting properties due to embedded light transmitting materials. Due to the small size of the fibres, they blend into concrete becoming a component of the material like small pieces of aggregate. This research work aims at investigating the effect of optic fibres on the strength and translucent properties of concrete. Fibre optics were introduced into the concrete mix as an optical material to enhance the translucency of concrete. The fibre optics were introduced at 2, 4 and 6% replacement level of fine aggregate. Compressive and translucency tests were carried out on the samples. From the test results it was observed that the compressive strength of translucent concrete increased by 4.3, 11.8 and 27.1% at 2, 4 and 6% optic fibre content respectively. The translucent concrete exhibited translucency property at different optic fibre content. The more the optic fibre the more translucency achieved as shown in the experimental result for example 135.26 lux at 6%, 85 lux at 4% and 55 lux at 2%.

Plastic optical fiber (POF) is highly appreciated for its applications in glowing textiles. However, fabricating thin POF with good side illuminating effect is a challenge due to the complicated manufacturing processes. CO2 laser treatment is normally applied to enhance the surface roughness without significant influence on other properties of materials. Titanium dioxide (TiO2) is widely studied for its high photo activity and thermal stability. The surface modification combined with TiO2 particles and CO2 laser treatment was carried out to investigate the side illuminating effect of POF. The images of surface morphology show that TiO2 particles reduce the thermal damage of POF surface during CO2 laser treatment. The results from side illumination testing prove that the employment of TiO2 particles, combined with CO2 laser treatment, could enhance the side illumination of POF for longer lasting application. Cyclic CO2 laser treatment can decrease the heat accumulation in POF and may...

CO2 laser treatment can increase the surface roughness of plastic optical fibres (POFs) with the diameter of 0.5 mm and enhance the input intensity and attenuation coefficient accordingly, which is supposed to weaken the side emission of POFs in long distance above 375 mm. TiO2 particles were applied to improve the increasing optical loss of POFs by laser treatment. POFs were first modified with fine TiO2 particles and then treated by CO2 laser with the pixel time from 30 to 120 ìs. The surface morphology was observed by scanning electron microscopy to investigate the changes of micro-structure before and after laser treatment and the distribution of TiO2 particles. The illumination intensity and attenuation coefficient were calculated and compared in two methods. It is visible that the evaluation by model LLF2 with two parts is more suitable for the fitting of experimental data and shows higher input intensity and lower attenuation than that by standard power function. Both the eva...

We investigate 40-Gb/s cost-efficient transmitter for access and metro networks. This 40-Gb/s transmitter comprises a standard directly modulated distributed-feedback (DFB) laser and a subsequent optical filter. Large dispersion tolerance of this transmitter is realized by chirp control through the phase correlation between adjacent bits for the destructive interference in order to erase the power of "0" bits while enhancing the extinction ratio. The chirp model of the DFB laser and the optimum parameters of the optical filter have been numerically analyzed. The chirp-managed 42.8-Gb/s transmission over 20-km standard single mode fiber (SSMF or SMF-28) without dispersion compensation and a centralized lightwave WDM-PON system are experimentally demonstrated. We have also realized the transmission over 100-m graded index plastic optical fiber (GI-POF). Moreover, the application in the metro network over 240-km SSMF or SMF-28 has also been investigated in this paper.

A simple configuration for the generation of a switchable dual-wavelength fiber ring laser is presented. The proposed configuration employs a short twin-core photonic crystal fiber acting as a Mach-Zehnder interferometer at room temperature. A polarization controller is further utilized to enable switchable dualwavelength operation.

A light intensity-modulated curvature measuring principle for gauging bending angles within a range between −120◦ and +130◦ based on speckle image processing is presented in this paper.Coherent light with a wavelength of 632.8 nm is propagated through a looped Polymeric Optical Fiber (POF) and received by a Charge-Coupled-Device camera (CCD), positioned on its end face.After applying a chain of image processing techniques the determination of the angle is realized by using the average of the pixel intensity and the amount of speckles within a Region Of Interest (ROI). Practical results revealed the existence of a non-linear dependence in the range of −120◦ and +130◦ between the geometrical arrangements of the POF, the average pixel intensity, the amount of speckles and the bent angle. Keywords— Polymeric optical fiber, POF, Curvature sensor, Bending sensor, Speckle image processing, Light intensitymodulated curvature sensor, Transmission loss sensor. Resumo— O presente trabalho apre...

This paper describes the development of a sensor designed to detect low concentrations of hydrogen fluoride (HF ) in gas mixtures. The sensor employs a plastic optic fiber (POF) covered with a thin layer of a glass-like material. The HF attacks the glass and alters the fiber transmission capability so that the detection simply requires a LED and a photodiode. The coated POF is obtained by means of a low pressure plasma enhanced chemical vapor deposition (PECVD) that allows the glass-like film to be deposited at low temperature without damaging the fiber core. The developed sensor will be installed in the recirculation gas system of the Resistive Plate Counter (RPC) muon detector of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) accelerator of the European Center for Nuclear Research (CERN).

A new simple and low-cost fiber optic sensor for cumulative detection of H 2 S and other sulphide compounds is described. The transducer is based on a plastic optical fiber and exploits a non-reversible chemical reaction, whose products interact with the evanescent field tails thus increasing the propagation losses with the exposure time. The sensor has a sensitivity of the order of few ppb.

This paper describes the development of a sensor designed to detect low concentrations of hydrogen fluoride (HF ) in gas mixtures. The sensor employs a plastic optic fiber (POF) covered with a thin layer of a glass-like material. The HF attacks the glass and alters the fiber transmission capability so that the detection simply requires a LED and a photodiode. The coated POF is obtained by means of a low pressure plasma enhanced chemical vapor deposition (PECVD) that allows the glass-like film to be deposited at low temperature without damaging the fiber core. The developed sensor will be installed in the recirculation gas system of the Resistive Plate Counter (RPC) muon detector of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) accelerator of the European Center for Nuclear Research (CERN).

A long-term multidisciplinary conservation study is actually in progress inside the Villa della Regina, a prestigious Savoy residence built in the seventeenth century and recently restored. The walls of some rooms of the Villa are decorated with precious tin-mercury mirrors, that are baked with a reflective coating constituted of a tin-mercury compound surrounded by liquid mercury. The reflective layer is very soft, thus any restoration is difficult to be performed and can lead to a complete destruction of the artifact. Amalgam corrosion is a very slow process and, although there is no way to prevent the oxidation of the reflective layer, the conservation state of the artifacts may be improved by keeping them in a controlled environment. For this reason, a monitoring system has been designed and installed that is based on a wireless network of extremely compact sensors, for temperature and relative humidity measurements. The sensors have been specifically designed to satisfy the requirements for use in cultural heritage field and the system allows one to automatically collect the data that can be analyzed with the final aim to establish a correlation between the environmental conditions and the conservation state of the artifacts. A restoration has been carried out by producing in situ an amalgam inlay on the corroded area to slow down the release of liquid mercury in order to avoid also possible unsafe conditions for staff and visitors. In addition,

A cumulative sensor for in situ monitoring of H 2 S vapors in museum showcases based on plastic optical fiber (POF) has been developed. H 2 S is responsible for the tarnishing of silver artifacts, so monitoring their total exposure over time to sulfide rich atmospheres can help in choosing the correct display procedure and, consequently, lead to improvements in their conservation. The sensor working principle is based on the modulation of the guided light intensity following a chemical reaction between a thin silver layer deposited onto the fiber core and the sulfide compounds to be detected. The proposed approach for the sensor fabrication requires the optimization of a two-step process: (1) etching of the fiber cladding to expose the core; (2) plasma deposition of a silver thin film onto the PMMA core. Silver was chosen as the sensitive element, since in the presence of H 2 S, it starts reacting immediately and loses its brightness with time proportionally to the concentration of the aggressive gas. Some prototypes of the proposed sensing system have been produced and tested in laboratory demonstrating the capability to detect H 2 S at concentrations of few part-perbillion (ppb).

We demonstrate that commercially available poly(D,L-lactic acid) (PDLLA) is a suitable material for the fabrication of biodegradable optical fibers with a standard heat drawing process. To do so we report on the chemical and optical characterization of the material. We address the influence of the polymer processing on the molecular weight and thermal properties of the polymer following the preparation of the polymer preforms and the fiber optic drawing process. We show that cutback measurements of the first optical fibers drawn from PDLLA return an attenuation coefficient as low as 0.11 dB/cm at 772 nm, which is the lowest loss reported this far for optical fibers drawn from bio-resorbable material. We also report on the dispersion characteristics of PDLLA, and we find that the thermo-optic coefficient is in the range of -10 -4 °C-1 . Finally, we studied the degradation of PDLLA fibers in vitro, revealing that fibers with the largest diameter of 600 µm degrade faster than those with smaller diameters of 300 and 200 µm and feature more than 84% molecular weight loss over a period of 3 months. The evolution of the optical loss of the fibers as a function of time during immersion in phosphate-buffered saline indicates that these devices are potential candidates for use in photodynamic therapy-like application scenarios.

An end-to-end transmission of coexisting multistandard radio (LTE, WiMAX, and UWB) signals is demonstrated for the first time with the transmission over a combined access and in-home networks consisting of 25-km SSMF, 25-m large-core diameter polymethylmethacrylate gradedindex plastic optical fiber link and 1-m wireless. The residential gateway includes O-E-O conversion to connect the access and in-home parts of the networks. This letter demonstrates a fully integrated radio signal distribution scenario from the central station to the end-user personal area networks.

Light emitting diodes (LED) are usually the alternative optoelectronic devices for optical communications with moderate bandwidth efficiency and bit rates, compared to semiconductor lasers. Laser applications dominate the long distance communication networks. However LED seems to be a very good solution, especially in very short distance communication networks, where Plastic Optical Fibers, (POF) are used as the optical transmission medium. This paper investigates a qualitative technique of calculating the bandwidth, based on first principles of semiconductor physics. This technique is more convenient for a first approach of the subject on optical communication networks and its simplicity provides a very useful analytical tool. Finally these results are compared with the existing experimental ones.

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Ribbon plastic optical fiber (POF) linked four-channel optical transmitter (Tx) and receiver (Rx) modules have been proposed and realized featuring an excellent alignment tolerance. The two modules share a common configuration involving an optical sub-assembly (OSA) with vertical cavity surface emitting lasers (VCSELs)/photodetectors (PDs), and their driver ICs, which are integrated onto a single printed circuit board (PCB) substrate. The OSA includes an alignment structure, a beam router and a fiber guide, which were produced by using plastic injection molding. We have accomplished a fully passive alignment between the VCSELs/PDs and the ribbon POF by taking advantage of the alignment structure that serves as a reference during the alignment of the constituent parts of the OSA. The electrical link, which largely determines the operation speed, has been remarkably shortened, due to a direct wire-bonding between the VCSELs/PDs and the driver circuits. The light sources and the detectors can be individually positioned, thereby overcoming the pitch limitations of the ribbon POF, which is made up of perfluorinated graded-index (GI) POF with a 62.5 μm core diameter. The overall alignment tolerance was first assessed by observing the optical coupling efficiency in terms of VCSEL/PD misalignment. The horizontal and vertical 3-dB alignment tolerances were about 20 μm and 150 μm for the Tx and 50 μm and over 200 μm for the Rx, respectively. The VCSEL-to-POF coupling loss for the Tx and the POF-to-PD loss for the Rx were 3.25 dB and 1.35 dB at a wavelength of 850 nm, respectively. Subsequently, a high-speed signal at 3.2 Gb/s was satisfactorily delivered via the Tx and Rx modules over a temperature range of 30 to 70°C with no significant errors; the channel crosstalk was below 30 dB. Finally, the performance of the prepared modules was verified by transmitting a 1080p HDMI video supplied by a Bluelay player to an LCD TV.

Background: Medical textiles offer a unique contact opportunity that could provide value-added comfort, reliability, and safety for light or laser-based applications. We investigated a luminous textile diffuser for use in photodynamic therapy. Methods:Textile diffusers are produced by an embroidery process. Plastic optical fibers are bent and sewn into textile to release light by macrobending. A reflective backing is incorporated to improve surface homogeneity, intensity, and safety. Clonogenic assay (MCF-7 cells) and trypan blue exclusion (NuTu19 cells) tests were performed in vitro using 0.1 g/ml m-THPC with three textile diffusers and a standard front lens diffuser. Heating effects were studied in solution and on human skin. PDT application in vivo was performed with the textile diffuser on equine sarcoids (three animals, 50 mW/cm 2 , 10-20 J) and eight research animals. Lastly, computer simulations were performed to see how the textile diffuser might work on a curved object. Results: At low fluency rate, there is a trend for the textile diffuser to have lower survival rates than the front lens diffuser for both cell lines. The textile diffuser was observed to retain more heat over a long period (>1 min). All animals tolerated the treatments well and showed similar initial reactions. The simulations showed a likely focusing effect in a curved geometry. Conclusions: The initial feasibility and application using a textile-based optical diffuser has been demonstrated. Possibilities that provide additional practical advantages of the textile diffuser are discussed.

In the modern day industries, Fiber optic transmission and communication are technologies that are constantly growing and support more challenges. Three properties of optical fibers are dispersion, absorption and scattering which cause attenuation and also decreased in transmitted power. To combat these losses and improve the reliability of fibers introduced many advanced technologies. Here two compensation techniques such as Fiber Bragg Grating and Optical Phase Conjugation are discussed with the help of simulation software "OPTSIM" to compensate dispersion. We have also analyzed the time delay of the received signal with variation of frequency by using B4530 trainer in the "Telecommunication Lab,

We propose to characterize optical power transmission in stepindex plastic optical fibers by estimating fiber diffusion and attenuation as functions of the propagation angle. We assume that power flow is described by Gloge´s differential equation and find a global solution that was fitted to experimental far field patterns registered using a CCD camera as a function of fiber length. The diffusion and attenuation functions obtained describe completely the fiber behavior and thus, along with the power flow equation, can be used to predict the optical power distribution for any condition.

In this paper, the application of a fiber Bragg grating written in a highly birefringent side-hole elliptical core optical fiber for two-axial strain measurement is presented. Hybrid optical fiber structures achieved by combining large side-holes and elliptical core result in a very high birefringence of 1 × 10−3 and thus high initial Bragg peak spectral separation of 1.16 nm, as well as a very high transverse force sensitivity, of up to 650 pm/(N/mm) or even −1150 pm/(N/mm), depending on the fiber orientation with respect to the applied force. Due to the ~22 %m/m GeO2 concentration in the core the fiber being highly photosensitive, which significantly simplifies FBG fabrication by UV illumination without the need for prior hydrogen loading, which worsens thermal stability. Finally, the developed FBGs written in the highly birefringent side-hole elliptical core optical fiber were embedded in the square composite plates and applied for strain measurements. Tests of two-directional fo...

This study reports use of inexpensive intensity‐based plastic optical fiber (POF) in the form of cantilever beam to monitor the force. The cantilever consists of POF surface bonded on the surface of metal beams viz. spring steel (SS) and mild steel (MS) and subjected to force. The performance of the force sensor is evaluated during macro‐bending caused because of the deflection of the beam by applied force. Experimentally obtained detector output of POF, which could be measured with negligible hysteresis is compared with finite element analysis in the range between 0.0098 and 19.613 N. The reproducibility of the sensor is observed in the limit of ±1%. The proposed sensor can replace stain gauge load cell to certain extent in some applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1020–1023, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24217

Concrete is traditionally a solid, substantial building material. It needs to makeover. Small buildings are replaced by high rise buildings and skyscraper. This arises one of the major problem in deriving natural light in building, due to obstruction of nearby structures. To overcome this problem, artificial sources are used to illuminate building, but artificial light leads to increase of heat level in the buildings. To evaluate the effectiveness of the smart transparent concrete, the present study aims at producing the concrete specimens by combining glass rods and optical fibers with different percentage and comparing it with the normal concrete. Two tests are carried out compressive test and light transmission test and cost comparisons are also done.

This work establishes computational analysis of relative refractive index property for light transmission via fiber optics using MATLAB simulation. Optical fiber is a dielectric wave guide which transmits signal with a low attenuation and dispersion at higher bandwidth or data rate. Recent advances in fiber optics introduced a largely new dimension into optical technology with the effect of improving transmission through the application of cladding system. Cladding in fiber communication is importantly applied to ease light transmission in the fiber-core interface by total internal reflection at the boundary between two light propagation region of a typical fiber. Optical fiber communication is a well recognized aspect of optical light transmission where clad fibers of different refractive indices recount for a measurable Numerical aperture and Acceptance angle in fiber networking and communication technology. This has lead to the efficient and effective optical transmission due to the adequate emergence and utilization of optical properties and parameters in optical fiber applications. A double cladding was set for the fiber and a maximum relative refractive index of 2.000% is obtained for an acceptance angle and numerical aperture range of 59°-64° and 0.859-0.900 respectively. This implies fast light transmission, high bandwidth and small bending sensitivity for fiber networking with applications in medicine and telecommunication compared to single cladding fiber.

Fiber-optic daylighting systems have been shown to be a promising and effective way to transmit sunlight in the interior space whilst reducing electric lighting energy consumption. To increase efficiency in terms of providing uniform illumination in the interior, the current need is to illuminate optical fiber-bundle with uniform light flux. To this end, we propose a method for achieving collimated light, which illuminates the fiber-bundle uniformly. Light is collected through a parabolic concentrator and focused toward a collimating lens, which distributes the light over each optical fiber. An optics diffusing structure is utilized at the end side of the fiber bundle to spread light in the interior. The results clearly reveal that the efficiency in terms of uniform illumination, which also reduces the heat problem for optical fibers, is improved. Furthermore, a comparison study is conducted between current and previous approaches. As a result, the proposed daylighting system turns out convenient in terms of energy saving and reduction in greenhouse gas emissions.

The goal of this project is to design and analyse a radio over fibre system for a four-story hospital with 20 rooms on each floor. The number of ONUs per floor is 20, and it was assumed that each room had an ONU capable of providing network access to voice, data, video, and biometrics. We build an 80-channel WDM optical transmitter using the WDM method. The proposed system includes a transmitter with 20 input channels, a multiplexer, a DE multiplexer, a 45-kilometer optical fibre, and an amplifier. The proposed model was simulated, and the results were evaluated in WDM systems using an optical amplifier. The receiver performance analysis of the Optical Communication System is shown by the BER simulation run and the eye diagram graphic, with the threshold set at 0.00120739. Furthermore, the eye height is 0.00141402, and the minimum BER is 5.59009e-006. When the simulated and calculated values of received power and total power loss are compared, the system is efficient.

A model is proposed to establish the relationship between the light coupling efficiency and fiber length for two contacted large fiber cores. The model correctly described the dependency of the coupled light on fiber length that was verified in the experiment with a twin-core fiber. This model can be used in fiber laser and erbium-doped fiber amplifier designs that employ twincore or multicore pumping.

Exposing an optical fiber core to the measurand surrounding the fiber is often used to enhance the sensitivity of an optical fiber sensor. This paper reports on the rapid fabrication of microstructures in an optical fiber using a CO₂ laser system which help exposing the optical fiber core to the measurand. The direct-write CO₂ laser system used is originally designed for engraving the polymeric material. Fabrications of microstructures such as in-fiber microhole, D-shaped fiber, in-fiber microchannel, side-sliced fiber and tapered fiber were attempted. The microstructures in the fibers were examined using a SEM and an optical microscope. Quality of microstructures shown by the SEM images and promising results from fluorescence sensor tests using in-fiber microchannels of 100μm width, 210μm depth and 10mm length show the prospect of this method for use in optical fiber sensor development. The direct-write CO₂ laser system is a flexible and fast machining tool for fabricating microstr...

Introduction During the last years, the standard step-index polymer optical fibre (SI-POF) with 1-mm core diameter has established itself as the preferred transmission medium for short-range optical data communications in automotive multimedia networks (MOST25/150) with data ...

This paper describes a multistandard fiber fed wireless system, which provides low-cost and enhanced performances regarding laser nonlinearity and RF transmitted power. Experimental results demonstrate that the proposed scheme provides not only optimized performances for low cost coming both from plastic optical fiber and vertical cavity surface emitting lasers (VCSELs), but also optimization of RF modulation power by complementary cumulative distribution function analysis and enhanced linear behavior by a whole new quasi-static approach of the VCSEL. With the help of those features, we successfully demonstrate minimization of error vector magnitude for simultaneous ultra-wideband multiband-orthogonal frequency division multiplexing and wireless local area network 802.11g optically transmitted signals and the possibility to use this system under conditions for symmetrical wireless communication. Index Terms-Complementary cumulative distribution function (CCDF), error vector magnitude (EVM), multiband-orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB), plastic optical fiber (POF), radio-over-fiber (RoF), vertical cavity surface emitting laser (VCSEL), wireless local area network (WLAN). I. INTRODUCTION T ODAY, higher and higher wireless data rate is required to give comfort to end users. Two main schemes for wireless in-home communications already exist: the IEEE 802.11 standard has being used since the end of the 1990s in wireless local area networks (WLANs), exhibiting a maximum data rate of 54 or 300 Mb/s with multiple input/output (MIMO) technology, and a coverage of about 100 m. Unfortunately, when one remote host uses a lower bit rate than the others, the performance of all hosts is considerably degraded [1]. IEEE 802.15.3c ultra-wideband (UWB) is an emerging technology for wireless personal area networks (WPAN), providing a high data rate-up to 480 Mb/s-but with a very small coverage, typically less than 10 m. This means that both solutions, WLAN and UWB, have to coexist for end users. Homes are being optically wired, if not already, to support digital traffic such as web navigation, video and audio broad-Manuscript

In this paper, we present a novel fabrication technique for constructing light focusing lenses, dielectric Fresnel zone plates on both flat wafers and tips of plastic optical fibers (POFs). SU-8 zone plate structures are made on glass substrate by photolithography with ink-printed soft mask, and then used as the template for hot embossing on the tip of PMMA POF. Focusing behavior for both 472 and 633 nm laser beams and LEDs in different colors are observed on glass wafers and POF tips, indicating that the proposed dielectric Fresnel zone plates can be built onto both substrate by a direct hot embossing process which may lead to a high volume production at low cost. Light intensity measurement on POFs proves that light focusing is achieved while intensity is maintained. This structure is expected to have broad applications in micro-imaging, micro-focusing as well as point-of-care medical surgeries.

This review paper gives an overview on Photonic Crystal Fiber (PCF) & its applications. Photonic Crystal Fiber is also known as micro structured or Holey fiber. Photonic crystal fiber is preferred over optical fiber because of its high design flexibility. Photonic crystal fiber is actually an optical fiber with a periodic arrangement of low index material in a background with high refractive index material. Light can be guided inside the PCF by either modified total internal reflection or photonic band gap guidance. Discussion of PCF in this paper includes its fabrication as well as application. Two methods namely "Stack and draw technique" & "Extrusion fabrication process" are used for the fabrication. PCF can be designed to get zero dispersion at required wavelength. PCF can be efficiently used in sensing applications using long period fiber grating (LPFG). LPFG can be fabricated using CO2 laser irradiation technique, which is preferred over interference method...

Impact of gamma radiation on transmission of a commercial Cytop polymer optical fibre (Lucina, Asahi Glass Company) is investigated. Spectral dependence of radiation induced attenuation in the investigated fibre is measured in the VIS-NIR spectral region. Besides attenuation increase, radiation is found to increase fibre susceptibility to water as well. While pristine Cytop fibre is rather humidity insensitive, strong humidity related absorption in the NIR region is observed after fibre irradiation. Selective irradiation of separate fibre sections is proposed as a way of fibre humidity sensitization and quasi-distributed water detection is demonstrated using optical time domain reflectometry at 1310 nm.

Reactive Powder Concrete (RPC) is a type of ultra-high performance concrete, this dense composite material generally characterized by high cement content, high durability, low porosity, low water/cement ratio and in most cases contains steel fibers as new types of concrete appears, further investigation for their mechanical properties are needed. This work aims to give a better understanding of RPC behavior by deriving formulas to calculate the modulus of elasticity and the splitting tensile strength in relation with compressive strength and steel fibers content. This study is based on data obtained from the experimental investigation done in this work and from others pervious works. The parametric study is based mainly on the silica fume content which is used in four different ratios (12 %, 15 %, 20 % and 25 %), the use of micro steel fibers 15 mm in length, 0.2 mm in diameter and aspect ratio of 75 added in ratios of (0 %, 1 %, 1.5 % and 2 %), and water/cement in ratios of (16 %, ...

In this work, a novel high birefringent (HiBi) fiber loop mirror sensor based on a "figure-of-eight" constructed with a 3×3 fiber coupler, is presented. The "figure-of-eight" is formed by two fiber loop mirrors (FLM's) made by four of the six fiber arms of the 3×3 fiber coupler. The other two remaining fiber ports of the 3×3 coupler are used as input and output fibers of the compound sensor. The sensing head is located in the one of the FLM and it is formed by a spliced section of HiBi elliptical core fiber. The spectral response of this "figure-of-eight" configuration presents two interference optical signals that can be easily tuned by a polarization controller that is located in the other FLM, and which is made only of standard singlemode fiber from two arms of the 3×3 coupler. The sensor head was optically characterized both in temperature and strain, showing wavelength dependence sensitivities of-0.23 nm/ºC and-2.6 pm/με, for temperature and strain, respectively. It is noticed that these sensitivities are practically the same for the two interference signals. Future work will explore the possibility to use the singlemode FLM to interrogate the sensor head made by HiBi fiber section, and providing elimination of phase fluctuations that can occur, increasing its potential for remote sensing applications.

Optical heterodyne communication systems using direct frequency modulated semiconductor diode lasers often exhibit system degradation because of the nonuniform injection current to frequency modulation (FM) transfer function present in most semiconductor diode lasers. In a frequency-shift-keyed (FSK) system, a nonuniform FM transfer function causes tone drift which results in increased crosstalk between tone slots and a corresponding degradation in system bit-error-rate (BER). Using simple passive electrical networks it is possible to equalize the nonuniform FM response and substantially reduce this transfer function induced BER degradation. The theory, computer optimization, construction, and test of various equalization networks and their use in realizing an FM equalized transmitter for a lOO-Mbit/s binary FSK communication system is described.

An easy-to-manufacture setup for a displacement sensor based on plastic optical fiber (POF) is analyzed, showing computational and experimental results. If the displacement is the consequence of force or pressure applied to the device, this can be used as a force or pressure transducer. Its principle of operation consists of bending a POF section around a flexible cylinder and measuring light attenuation when the whole set is subjected to side pressure. Attenuations are obtained computationally as a function of side deformation for different design parameters. Experimental results with an actually built prototype are also provided.

Fiber-optic daylighting systems have been shown to be a promising and effective way to transmit sunlight in the interior space whilst reducing electric lighting energy consumption. To increase efficiency in terms of providing uniform illumination in the interior, the current need is to illuminate optical fiber-bundle with uniform light flux. To this end, we propose a method for achieving collimated light, which illuminates the fiber-bundle uniformly. Light is collected through a parabolic concentrator and focused toward a collimating lens, which distributes the light over each optical fiber. An optics diffusing structure is utilized at the end side of the fiber bundle to spread light in the interior. The results clearly reveal that the efficiency in terms of uniform illumination, which also reduces the heat problem for optical fibers, is improved. Furthermore, a comparison study is conducted between current and previous approaches. As a result, the proposed daylighting system turns out convenient in terms of energy saving and reduction in greenhouse gas emissions.