This paper proposes an innovative approach of manufacturing optical fibers using nozzle-mask-aided additive manufacturing. Nozzle-masks ease 3D-printing of optical fibers allowing the manufacturing or drawing of optical fibers of up to 10 μm diameter. These nozzle-masks feature a suction mechanism to prevent clogging of printhead and mask. The extrusion of Polymethyl-methacrylate material through the print-head and nozzle-mask simplifies the rapid prototyping of the optical fibers.
The ability to manufacture complex 3D-objects directly from its CAD model is the important reason why additive manufacturing is being widely used to fabricate cost-efficient prototypes and preferred over conventional manufacturing methods. Moreover, it portrays as a bridging technology to connect different scientific and industrial fields, e.g. Engineering, Medicine, etc. Consequently, additive manufacturing finds its applications in the production of patient-specific orthoses. This paper discusses the development of a pressure sensor based on an optical waveguide principle manufactured using stereolithography apparatus process to embed into a below-knee orthosis. For Orthopedic patients, the below-knee orthosis must be adjusted to the lower leg at regular intervals due to anthropometric changes in patient’s body to achieve proper mobility and correct load. Currently, this alteration relies on the patient’s estimation of support load which is only sub-optimal. Hence, the concept of developing an intelligent orthosis with a novel embedded optical system to monitor the exact support load at the neuralgic is proposed.
Additive manufacturing enables direct prototyping of complex 3D-objects that are difficult to manufacture using conventional methods. It is widely used to fabricate cost-efficient prototypes and portrays as a bridging technology to connect different scientific and industrial fields, e.g. Engineering, Medicine, etc. Consequently, additive manufacturing finds its applications in the production of patient-specific orthoses. This paper discusses the application of the stereolithography apparatus process to develop a pressure sensor based on an optical waveguide principle to embed into a below-knee orthosis. For Orthopaedic patients, the below-knee orthosis must be adjusted to the lower leg at regular intervals due to anthropometric changes in patient’s body to achieve proper mobility and correct load. Currently, this alteration relies on the patient’s estimation of support load and is only sub-optimal. Hence, the concept of developing an intelligent orthosis with a novel embedded optical system to monitor the exact support load at the neuralgic is proposed.
Visible light communication (VLC) allows the dual use of lighting and wireless communication systems by modulation of illumination devices. However, to increase the performance, typically, beam-forming measures are taken creating pencil beams, thus contradicting the illumination purpose. In order to optimize the performance trade off between efficient illumination and communication, the switching capabilities of illumination LEDs are examined. Illumination LEDs with standard drivers and without beam-forming show limited applicability for communication purposes as they are not optimized for the necessary switching capability (f ≈11 MHz) and coherence. Methods to enhance the electrical current by pre-equalisation, biasing, carrier sweeping and current shaping are examined in respect to the illumination LED's communication performance. A novel driver scheme is derived which achieves considerably higher switching frequencies (f ≥100 MHz) without employing beamforming at the illumination LED. This driver is able to obtain a data rate of up to 200 Mbit/s at a distance of 3.2 m, using on-off keying (OOK) modulation technique. Therefore, it is feasible to apply the LED driver by implementing standardised illumination devices in VLC systems.
Additive manufacturing (AM) and rapid prototyping process (RPP) have revolutionized the production of 3D objects in the last few decades. RPP has considerably increased the rate of production and the possibility of manufacturing prototypes in the fields of electrical, optical, and mechanical engineering. The manufacturing of optical prototypes including spherical, aspheric, and special kinds of lenses and lens arrays has reformed the fabrication of optical components. In this paper, specifically designed lens array prototypes for application in visible light communication (VLC) are introduced. These lens array prototypes are manufactured using the stereolithography apparatus (SLA) process. These lens arrays are designed to achieve optimal transmission of the light beam for VLC systems. One of the prototypes from the lens arrays contains primarily four spherical lenses and one thicker convex lens and the other contains one fresnel lens as a substitute for thicker convex lens. These lens arrays are further post-processed to achieve the required transparency. These lens array prototypes are tested using laser and LEDs. The ON-OFF keying modulated light beam was transmitted through the lens array at the sender side and focused on the photo-receiver using another lens array at the receiver side which is 200 cm apart. After evaluating these lens prototypes, it can be concluded that with appropriate post-processing and high-resolution stereolithography based manufacturing, a low data rate VLC link can be formed.
Additive manufacturing (AM) has provided a new aspect of manufacturing 3D objects in the past few decades. The use of AM for the production of 3D objects has accelerated the rate of designing and manufacturing. These AM techniques can be utilized in manufacturing optical, mechanical and electrical prototypes. The manufacturing of optical prototypes involves the production of spherical lens prototypes and special forms of aspheric and concentrator lenses such as fresnel lens prototypes. Different designed fresnel lens prototypes are manufactured using a transparent clear resin material and stereolithography apparatus (SLA) process. It uses a photochemical process to develop 3D structures. These manufactured fresnel lens prototypes are difficult to postprocess using hand polishing, hence they are post-processed using lacquering to get more transparency. These prototypes are tested using a laser source to evaluate the attenuation of light and focal length of manufactured fresnel lens prototypes. Similar tests using a commercially available convex lens of the same focal length are carried out. The results of these tests show that the difference between the mean of attenuation of light beam when passed through a fresnel lens prototype and the convex lens is 1 dB. The focal length of manufactured fresnel lens prototypes has a 10 mm deviation. Therefore, it is feasible to manufacture complexity and cost reduced fresnel lens prototypes using SLA and lacquering.
Today radio based wireless communication technologies offer limited performance, whereas optical wireless com- munication systems (OWC) propose potentially a high performant, scalable communication system conforming to real time conditions. However, current studies imply, that OWCs still lack the necessary performance and robustness level for most wireless applications in industrial production environments. In this approach several types of noises for free-space optical communication systems are empirically analysed in an accredited, exemplary industrial production environment. While the channel noise is usually modelled by the signal to noise ratio it is found that real environments cannot be approximated by the usual static additive white gaussian noise. In this approach the accumulated measurement data represents the spectrum variation of different locations and times relating to different types of noise sources. The implementation in a total channel model allows the optimization of OWC designs like the channel access scheme or the modulation type concerning performance and robustness. Furthermore an additional measurement setup is proposed, capable of measuring and classifying existing noise sources in order to serve the design of OWC systems in industrial production environments.
In the context of the fourth industrial revolution and the related development towards self-organizing processes, innovative and advanced production technologies with completely new approaches are required. Modern additive manufacturing (AM) technologies contribute to this with their advantages like freedom of design, cost-efficient product individualization, and functional integration. By using these technologies, the fabrication of the quantity of size one and also the manufacturing of problem adapted, demand driven or requirement adapted components are possible. One promising AM technology is the fused layer modeling technology (FLM). The desired components are produced by the direct solidification of an extruded and heated filament material. Modern FLM printers are able to use two or more nozzles and therefore enable the use of two or more different filament materials within one printing job. Applying simultaneously various materials, it is feasible to print components with additional functionalities. Currently, filament materials exist that are transparent within the wavelength of optical sensor systems and optical communication systems. Combining transparent and non-transparent materials or materials with different numerical indices, it is possible to manufacture light-guiding structures which inherit all of the above mentioned capabilities of AM. In this paper, the application of FLM technology to print light-guiding structures with a defined 3D trajectory is analyzed. At first different transparent filament materials are analyzed. Then first straight test structures consisting of one optical transparent material with a variation of the number of strands are defined and printed. The core cross-section, the fusion of different strands and the attenuation of these structures are analyzed. Based on the positive results of the latter different structures with embedded optical waveguides are printed. After this, the course of the trajectories, the core cross-section, and the attenuations are analyzed by measurement. Due to the promising results, the first prototype towards a sensor application is manufactured and analyzed by measurement.
This paper presents a bidirectional optical data transmission system as an enhancement of a contactless power transmission system (CPTS). The latter consists of two separate devices and is able to transmit up to 240W of electrical power using inductive resonant coupling. The optical system consists of two self-developed light-guiding structures and a short-reach free-space optical path. As source and sink of the optical system a light-emitting diode resp. a photodiode with a centroid wavelength of 850nm are used. The optical system is positioned within the CPTS; it transmits the PROFIBUS protocol. Due to the restrictions given by the applications areas of the CPTS, such as air gap up to 5°mm, misalignment up to 2 mm, tilting up to 5 and rotation angle up to 360°, different kinds of light-guiding structures are analyzed by simulation. Based on these results the most promising structures are selected and manufactured. Hereafter the attenuation and the near field characteristic of one light-guiding structure is analyzed. After this, the attenuation based on misalignment, variation of air gap, tilting and rotation between two light-guiding structures are analyzed by measurement. To check whether the requirements of the PROFIBUS has been satisfied by the complete data transmission system, the transient transmission behavior of the system was analyzed by a pseudo-random bit stream. In this paper the most important results of the design, the simulation and the measurement are explained. The presented results demonstrate the ability to design of such systems based on simulations and to evaluate the suitability of various geometries for present and future works.
Optical interconnects on printed circuit board level are a promising choice to support high bandwidth for short distance interconnects. These interconnects consists of highly multimode step index waveguides with rectangular core cross sections. Therefore ray tracing is an excellent method to determine the optical path parameters, e.g. optical power, ray path lengths and local ray directions. Based on these parameters the step response, the transient transfer function and the coupling behavior can be calculated. Classical ray tracing methods calculates the optical path parameters of each ray by successively computing internal reflections until a termination condition is reached. Therefore the computing time depends on the number of internal reflections. If the optical waveguide consists of cascaded straight and curved segments, e. g. point-to-point interconnects, one can use the analytic ray tracing method to determine the optical path parameters. The whole path parameters of each ray are determined by one analytical computation. The computing time depends on the number of segments. The analytic ray tracing method is unusable to determine ray path parameters of segments with varying core cross sections, e.g. tapers, crossings, splitters and combiners.
A Proof-of-Concept for a multi-channel WDM board-level optical communications link is under development. This
paper is focusing on theoretical and experimental evaluation of thin-glass based nearly single mode graded index optical
waveguides with regard to low loss in the 1310nm regime. Results from waveguide characterization will be reported.
Waveguide modes are determined theoretically from the measured refractive index profiles. Towards improvement of
the robustness of the coupling efficiency against misalignments, investigations on the use of tapered waveguide
structures will be presented too.
Modal noise is an undesired modulation of the guided light intensity in a multimode waveguide. Applying the frequency correlation function the frequency dependence of this noise as well as the bandwidth of a multimode waveguide can be estimated. In this paper the existing model of the frequency correlation function for a waveguide with smoothed dielectric interfaces is enhanced to analyze the influence of surface roughness on the achievable bandwidth. This surface roughness is caused by the manufacturing process of the waveguides.
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