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In this article, we give an overview of the development of an asymmetric optical bus coupler (AOBC) from the theoretical basis, the optical continuous wave, and bit rate performance to the implementation in a 3-D-Opto-MID package. The coupler allows for an interruption-free and bidirectional connection between two multimode waveguides, with different coupling ratios at the same node up to an aspect ratio of 5:1 depending on the coupling direction. For the first time, data transmission up to 12.5 Gbit/s is demonstrated with the AOBC, as well as the full implementation of the coupling element into a 3-D-Opto-MID package including an electrical test circuit.

This article presents an innovative way for additive manufacturing of optical multimode waveguides for short range data transmission. By the use of aerosol jet printing between conditioning lines on flexible foils, low cost, and low weight polymer optical waveguides can be easily fabricated. The main advantages – compared to other waveguide manufacturing techniques – are the maximum fabricable waveguide length (not limited by panel- or wafer size), technology costs and 3D-ability. Furthermore, the printing allows for very long structures, which are not limited to wafer or panel sizes. In order to classify the new manufacturing approach and compare it to other technologies such as photolithography, imprinting, dispensing and ion-exchange, results on the mechanical (shear strength) and optical performance (transmittance, near field and attenuation) are presented. In addition, the experimental results on the data transmission performance are important to prove the suitability of the waveguides for high-speed communication applications. In this context, nearly error-free transmission up to 10 Gbit/s was achieved at a wavelength of 850 nm.

Understanding how engine design and operation affect blow-by aerosol characteristics is key to reducing the emission of particulate matter (PM) via the crankcase ventilation system. To this end, representative aerosol data from four different diesel engines are compared on the basis of brake mean effective pressure (BMEP) and engine speed. The data were obtained from comparable sampling positions, using the same sampling system and optical particle counter. The discussion is based on the narrow particle size range of 0.4–1.3 µm, chosen for its significance with regard to blow-by aerosol sources, as well as for the challenges it poses for separation systems. Key findings include particle size distributions (PSD) of virtually identical shape, indicating that these engines share the same aerosol sources and underlying generation mechanisms. However, absolute concentrations differed by a factor of about six, presumably due to differences in engine design, which in turn affect key parameters such as temperature, pressure and flow rates. At BMEPs ≤ 10 bar all engines exhibited similarly low aerosol concentrations. With increasing BMEP the concentration rose exponentially. The engine with the smallest rise and the lowest total concentration featured an aluminum alloy piston, the smallest displacement, the lowest peak BMEP as well as the lowest maximum oil temperature. At maximum torque the aerosol concentration scaled fairly linearly with engine displacement. Increasing the engine speed had a minor impact on aerosol concentrations but affected blow-by flows, hence leading to a rise of aerosol mass flows. Within the limits of this comparative measurement studies, three generation mechanisms are provided for blow-by aerosols.

A novel coupling approach with specific coupling ratios depending on the coupling direction (optical bus to electro-optical device and vice versa) is presented. According to that, an asymmetric optical bus coupler (AOBC) is obtained, where a high amount of light is coupled from a device/module into the optical bus, whereas the ratio in the opposite direction is significantly smaller to keep enough energy in the bus for later coupling. This is realized without any filters by a specific bending of the waveguides. Hence, an up to four times higher coupling ratio in the module-to-bus direction is achieved compared to the opposite direction at the same junction. In contrast, current coupling schemes have a 1:1 coupling, waveguides are interrupted or filters are used. In this paper, we investigate the influence of temperature on the AOBC. For that, we constructed a special measurement setup, which allows for a controlled temperature change only at the coupling point. With this setup, we investigated the influence of temperature (up to 80°C) on the bus coupling over 48 hours. The measurements revealed, that the coupling power rises with increasing temperature and vice versa. With an additional vision system, we observed the enlargement of the contact area of the waveguides (coupling area), because of thermal expansion, which leads to the change of the coupling power. Besides this variation, the coupling point is damaged at 20°C/80°C cycles because of the high mechanical load. However, at 20°C/60°C cycles, the AOBC is stable over the measuring period.

This paper discusses a novel packaging approach for electro-optical (E/O) co-integration of IC-chips to realize hetero-integrated transceivers for optical chip-to-chip (C2C) communication. For an integration of chip-components into optical transceivers a polymer package fabricated using additive manufacturing methods are applied. Based on two optical transceiver assemblies - VCSEL-based and Si-photonic-based - different requirements on the package are discussed. For the Si-photonic chips measurements on the lateral and angular misalignment requirements have been performed. The results of the characterization of grating couplers show that the maximum lateral misalignment for 1dB-loss vary between ± 1 µm and ± 3.5 µm. For the angular sensitivity the 1dB-tolerances of +/- 2° at the in-coupling interface and of about +/- 0.4° at the out-coupling have been measured. The simultaneous IC-device embedding and chip-carrier fabrication using casting method is proposed. By subsequent build-up of dielectric/metal multilayer stack an electrical and optical redistribution network for routing of both optical and electrical signals can be realized. A hybrid polymer Ormocer® material has been applied as optical and dielectric material enabling the E/O co-integration using one material class. The performance of this material in both domains optical and RF has been proven. Based on attenuation measurements of multimode optical waveguides low-loss transmission of < 0.05 dB/cm at 850 nm wavelength has been shown. Based on transmission-line (TL) measurements in the frequency range of 140 GHz to 220 GHz the superior dielectric properties with TL-losses of about 1.1 dB/mm have been achieved.

This contribution discusses technology development for the realization of chip-to-chip interconnection based on flexible optical waveguides. Two approaches for optical coupling between waveguides and active devices are presented. Both approaches built on the planar polymeric optical multimode waveguides integrated on flexible substrates (PEN-foil). This waveguides structured using UV-photolithography and Ormocere-materials feature low optical attenuation below 0.05 dB/cm. The first approach for coupling between optical waveguides uses a bidirectional interruption-free waveguide coupler. The principle bases on directional core-core-coupling and allows for adjustable coupling ratio by tuning the overlap area. In addition, an asymmetric coupling behavior depending on the coupling direction due to a bending of one of the coupling waveguides is achieved. This coupling method shows supremacy for optical bus systems where tunable, asymmetric coupling ratios are desired. The second optical coupling approach for waveguide-to-chip coupling bases on out-of-plane optics. Direct integration of 45° micro-mirrors into polymer waveguides using dicing process is investigated. Two approaches for optoelectronic (OE) subassembly with flexible optical waveguides are considered one with flip-chip bonded and one with embedded OE-devices. Using optical characterization the influence of fabrication parameters on the optical performance of diced mirrors with insertion power loss measurement is derived and presented.

In this paper, we present a bidirectional interruption-free multimode waveguide coupler for optical bus systems on board and module level. The principle is based on directional core–core coupling and allows for adjustable coupling powers by tuning the overlap area. By adding a bending to one of the coupling partners, it is possible to obtain specific asymmetric coupling rates depending on the coupling direction (module to bus or vice versa). The proposed approach is extensively analyzed by optical simulation (beam propagation method) and measurements including experiments on the attenuation, the coupling rate, and the bit rate performance.

In order to build high performance 3D-Opto-mechatronic integrated device packages, we demonstrate the direct stereolithographic printing of polymeric resins onto ceramic substrate. The effects of adhesion are examined, the lower size limit for structures is found and the adhesion strength is measured. With the results a suitable combination of materials can be chosen for creating a hybrid package for a 3D-Opto-mechatronic integrated device. A prototype of an optical coupler is printed successfully and shows one possible application.

In this article, we present a coupling concept for an interruption-free asymmetric bidirectional optical bus coupler for board and module level. With this approach, it is possible to connect several electro-optical devices to a single waveguide. A core-to-core connection principle is used, where the cores get into physical contact at their side faces. The coupling ratio can be tuned by adjusting the overlap area of the two cores with different contact pressures. Because of a bending in one of the waveguides, it is possible to achieve a specific asymmetric coupler design, where the coupling ratio depends on the coupling direction (bent waveguide to rigid one or vice versa). To derive design rules for prototyping, a simulation is performed using two different independent approaches for cross-checking. With a ray tracing simulation, coupling ratios and energy distribution within the bent core are analyzed. In addition, a simulation with the beam propagation method is used to take wave optical effects into account as well as to establish a holistic view on the coupling concept.

In this work we present the additive manufacturing of optical multimode waveguides on flexible foil by aerosol jet printing. In order to obtain higher aspect ratios for the waveguides, the foils are conditioned by a flexographic printing step in advance. This technique is used to manufacture asymmetric bus couplers, which allow for coupling without waveguide interruption. They follow the working principle of directional core-core-couplers but have different coupling ratios depending on the coupling direction, due to a bending of one of the coupling partners. The latest results on the printing process are shown, especially the laser structuring of the flexographic printing form to optimize the condition lines. Also the attenuation of the printed waveguides is measured as well as the coupling results of the asymmetric bus coupler. Especially the coupling powers and the strength of the asymmetric effect are shown.

In this work we discuss optical coupling technologies for the manufacturing of out-of-plane optics integrated in planar waveguide for interposer-and board-level. Each technology is evaluated on a silicon interposer with optical dielectric through silicon vias (TSV) with SU8 (core) and SiO2 (cladding). First, applying a nanoimprint technology a polymer waveguide has been created with round-shape curvatures to realize focusing of the light, which enhances the coupling efficiency. Furthermore due to the round shape the light is focused in the waveguide to reduce the transmission losses. Additionally as a second technology a moving mask method is shown to achieve a tilted mirror face by this special exposure procedure for better compability of mirror fabrication with lithography processes. As a third technology the mirror fabrication by dicing into a polymer waveguide has been applied, which results in a V-groove mirror. The feasibility of all fabrication technologies have been performed on rigid substrate. For enhanced yield of electro-optical system implementation of out-of plane optics on flexible substrate has been performed. In this case diced mirrors have been manufactured on polymeric waveguides with Ormocere® on a flexible PEN-foil. The influence of dicing blade on optical losses caused by the scattering on rough diced mirror surface has been analyzed. The min. power losses of the diced mirror of 0.22 dB have been measured.

Goal of the presented work is the development of an optical bus-coupler, which enables easy connection between two waveguides without interrupting the bus. It is possible to realize optical bus systems by connecting several modules onto one waveguide with a core-core-coupler. In this paper we present the concept of a bus-coupler, which is suitable for a bidirectional coupling with a definable ratio. In order to tune the coupling efficiency bended flexible planar waveguides are used, which are pressed onto the bus with a defined force adjusting the overlap area of the two coupling waveguides. We will introduce the manufacturing of the multimode waveguides on flexible substrates by photolithographic structuring. Furthermore, we present results of our investigations on the behavior of planar waveguides under bending in terms of optical losses and power distribution within the waveguide core. Based on the experimental results we will derive the requirements and design rules for the coupling element.

In our work an optical bus-coupler is proposed, which enables easy bidirectional connection between two waveguides without interrupting the bus using a core-to-core coupling principle. With bended waveguides the coupling ratio can be tuned by adjusting the overlap area of the two cores. In order to ensure large overlap areas at short coupling lengths, the waveguides have rectangular cross sections. To examine the feasibility of this coupling concept a simulation was performed, which is presented in this paper. Due to multimode waveguides, used in short range data communication, a non-sequential ray tracing simulation is reasonable. Simulations revealed that the bending of the waveguide causes a redistribution of the energy within the core. Small radii push the main energy to the outer region of the core increasing the coupling efficiency. On the other hand, at excessive lowered bend radii additional losses occur (due to a coupling into the cladding), which is why an optimum has to be found. Based on the simulation results it is possible to derive requirements and design rules for the coupling element.

Research for new production chains in the field of waveguide fabrication is a challenging task. Realizing a cost efficient manufacturing process allows integrating optical data communication in arbitrary structures, for example, the wing of an airplane or the body of a car. The production chain described in this paper contains the design, simulation, and fabrication process of printed polymer optical waveguides (POWs).