Optical data links and bus systems are becoming increasingly attractive for automobiles. In 1998, a first optical data bus system, based on polymer optical fibers and visible light-emitting diodes was introduced in Mercedes-Benz cars to interconnect information and entertainment devices within the passenger compartment. Since 2002, media-oriented system transport (MOST) is the standard for an optical infotainment data bus system in the automotive industry. However, with increasing demands on network flexibility, robustness, safety-relevant functions, and data rate, the currently used technologies reach their limit. A new physical layer, based on 200-/spl mu/m polymer-cladded silica fibers and infrared-emitting vertical-cavity surface-emitting lasers, is a promising solution. This paper provides an overview about the state-of-the-art physical layer of standard MOST data bus systems, shows its limitations, and presents new optical-physical-layer concepts for next-generation data bus systems in cars.

Optical data links and data bus systems are increasingly attractive in vehicles. After the successful introduction of the first systems in 1998 by Mercedes Benz, today optical data buses are common in more than 20 different vehicles. All currently used systems are based on polymethyl methacrylate (PMMA) optical fibers and red light emitting diodes (LEDs). They are limited to a temperature range below 85/spl deg/C, moderate data rates below ca. 100 Mbit/s and short point-point-links. We investigated new physical layer approaches, both based on polymer fibers as well as on large core silica fibers. A system based on polymer cladded silica (PCS) fibers and vertical-cavity surface-emitting laser (VCSEL) diodes can be used up to data rates of 1 Gbit/s in all relevant installation areas of cars or trucks. In addition it allows new system architectures and new wiring concepts for the future and therefore has the potential to be the common and scalable physical layer for all future high data rate bus systems, e.g. drive-by-wire systems or video based driver assistant systems in cars and commercial vehicles.

In Fahrzeugen verwendete elektrische und optische Verbindungstechniken stossen heute zunehmend an ihre technischen und wirtschaftlichen Grenzen. Das hier vorgeschlagene, untersuchte und prototypisch realisierte optische Verbindungssystem auf Basis von Mehrmodenquarzglasfasern mit Polymermantel und oberflaechenemittierende Laserdioden mit Vertikalresonator hat das Potenzial, diese Grenzen zu ueberwinden und eine skalierbare und gemeinsame physikalische Busschicht fuer zukuenftige hochbitratige Datennetze in allen relevanten Fahrzeugeinbauraeumen zu werden. Moegliche Einsatzbereiche sind Telematiksysteme, Drive-by-wire-Systeme, Sensornetzwerke und videobasierte Sensornetzwerke. (A) Beitrag zur Tagung Technologien in der Fahrzeugtechnik des VDI Kompetenzbildes Optische Technologien, 17. und 18. Juni 2003, Baden-Baden. Siehe auch Gesamtaufnahme der Tagung, ITRD-Nummer D351861.

We have investigated the design and the fabrication of planar transmissive and reflective star couplers for 200 /spl mu/ polymer clad silica (PCS) fibres. We propose the design of potential low-cost planar optical star couplers and demonstrate prototypes with good optical performance.

Robust, high speed optical data bus systems are increasingly required in automobiles, not only for entertainment applications within the passenger compartment but also for engine management systems and safety sensor networks. Optoelectronic components and modules intended to be used in cars have to withstand harsh environmental conditions, e.g. they have to be operational within a wide temperature range of up to -55 degreesC to +125 degreesC for several thousand hours and at the same time they have to be of very low-cost. In this paper we describe a 500 MBit/s transmitter module based on a commercial available 850 rim vertical-cavity surface-emitting laser and a bias-T driving circuit. The optical output power of the module varies only by -0.5 dBm +/- 1 dB in the required temperature range without active temperature control. In addition we describe a packaging solution for the VCSEL transmitters allowing the operation of the module even in an extreme engine compartment environment, where short term temperature peaks above 125 degreesC appear.

Here we present an optical transceiver concept for a reflective star bus system, showing favorable properties in respect to coupling efficiency and packaging. It is based on a hot embossed polymer substrate with two integrated micro-mirrors and a waveguide. On top of the substrate, above the mirrors, a vertical-cavity surface-emitting laser diode (VCSEL) and a photodiode chip are mounted with a flip-chip technique. At the end face of the waveguide a Polymer Clad Silica (PCS) fiber with a core diameter of 200 μm is attached in a groove. Thus an easy assembly of the individual components and a compact package is achieved. To evaluate and optimize the efficiency of the transceiver module we performed extended ray tracing calculations. Included are coupling efficiency between fiber and planar waveguide as well as coupling efficiencies between VCSEL and waveguide and between waveguide and photodiode, respectively. For a realistic estimation we took the transverse mode emission behavior of VCSELs at different supply currents and temperatures into account. Therefore we measured far-fields of VCSEL chips mounted on a heat sink for temperatures up to 85 °C and included the results in the simulations. The calculations indicate that the temperature dependant output power of the VCSEL is partly compensated by the variation in coupling efficiency. Measured VCSEL to fiber coupling efficiencies of about 60 % and out-coupling efficiencies to the photodiode of 70 % are achieved, in good agreement with calculations. Therefore our compact and low-cost concept shows at least 2 dB lower insertion losses compared to conventional 3 dB coupler solutions.

The invention relates to a lighting means for the interior of vehicles, which is additionally useful as optical data interface to mobile electronic devices as well as repeaters for signal transmission between two or more mobile electronic devices by means of a suitable control unit, as well as equipped with the illumination device the vehicle and a data communication system for the interior of vehicles, which uses the illumination devices mentioned.

Optical data links and data bus systems are increasingly attractive in vehicles. After the successful introduction of the D2B optical system in Mercedes cars a next generation data bus for telematics applications, the MOST bus, was chosen not only by DaimlerChrysler but also by several other automobile manufacturers. It is expected that the data rate of 22.5 M bit/s will be enhanced in the intermediate future up to above 100 M bit/s for infotainment applications and to even higher data rates if video processing systems are installed in safety relevant driver assistance systems. In this article, today's and future demands on the physical data bus layer in cars are described, the currently used technology approach based on polymethylmethacrylate fibers is shown, and future physical layer solutions are discussed.

Since 1998 the first optical data buses, based on a ring topology and polymethylmethacrylate (PMMA) fibers with 1 mm core diameter and red emitting LEDs were introduced in cars to interconnect information and entertainment components. These systems currently are limited to the passenger compartment, because PMMA fibers do not tolerate environmental temperatures above 85 /spl deg/C, the data rate of these systems is limited to well below 100 MBit/s and the ring topology does not allow the interconnection of safety critical control units. Optical datacom buses based on standard multimode fibers are not useable in cars because of the severe environmental conditions and because of the extremely low-cost demands for in car data transmission systems. We propose and demonstrate a star coupled data bus system based on 200 /spl mu/m core diameter hard clad silica (HCS) fibers for 16 terminals with a data rate of up to 200 MBit/s.

The authors demonstrate that the requirements of optical data buses in mobile systems will increase dramatically in the coming years. Beside 650 nm resonant cavity LEDs in combination with PMMA fibers, 850 nm VCSELs with 200 /spl mu/m core diameter HCS fibers are most attractive. High data rates can be achieved, insertion losses are low, a large temperature range can be tolerated and large VCSEL-fiber and fiber-fiber alignment tolerances allow low cost connectors.

We report a detailed study on the transverse mode behavior of vertical-cavity surface-emitting lasers (VCSEL's) under strong external feedback, Backreflections from a glass-facet result, periodically depending on the feedback phase, in variations of the transverse mode pattern of strongly index guided multitransverse-mode-emitting lasers, As a result, butt-coupling efficiencies of these lasers strongly depend on laser-fiber distance, For typical active VCSEL diameters around 15-mu m fiber-coupled powers into standard 50 mu m-core diameter graded-index (GI) silica fibers vary by nearly 10 dB, Even far high-numerical aperture 100-mu m-core diameter fibers, power variations of up to 2 dB are observed.

We report a detailed study on butt-coupling efficiencies of vertical-cavity surface-emitting lasers (VCSEL's) to standard graded index multimode silica fibers, Coupling efficiency strongly depends on active laser diameter as well as index guiding and transverse mode spectrum of the laser. For typical active laser diameters of 16-20-mu m coupling efficiencies of about 90% are obtained with weakly index guided proton-implanted vertical-cavity lasers (VCL's) whereas stronger index guided oxidized lasers show considerably lower coupling efficiencies between 75% and 55%, depending on driving currents.

We have proposed and demonstrated a new low-cost, low insertion loss and compact optical transceiver module for optical data busses with reflective star topology. System experiments show the feasibility of these modules as transceivers in control data busses for mobile systems. We believe that the described mounting technique can also be applied to 50/125 /spl mu/m and 62.5/125 /spl mu/m silica and to plastic optical fiber based systems.

Vertical cavity laser diodes (VCSELs) form a new class of semiconductor lasers extremely prospective for a wide range of applications, e.g. in parallel fiber links, optical interconnects and cross connects, bar code scanners, compact optical disk systems and laser printers. Parallel fiber busses using VCSEL transmitters have just entered the market. Compared to conventional edge emitting laser diodes VCSELs have distinct advantages like low divergence, astigmatic-free output beams for efficient fiber coupling or dynamic single-mode emission up to 40 Gbit/s data rates under direct modulation. Two-dimensional independently addressable laser diode arrays are easily produced and may be applied for display or monitoring purposes or coupling to fiber bundles. Like light emitting diodes VCSELs are manufactured on wafer scale and testing is also performed directly on-wafer. This is in contrast to edge emitting lasers where cleaving is required and testing is performed after dicing and facet coating which leads to comparatively high fabrication costs. Moreover, mounting and packaging requirements are expected to be much less for VCSELs than for edge emitters.

The fabrication and testing of very uniform, planar proton-implanted independently addressable 10x10 vertical-cavity surface-emitting laser diode arrays is reported. Individual elements of 12 mu m active diameter show threshold currents around 4 mA and emit up to about 300 mu W single-mode. An electrical 3 dB modulation bandwidth of 4.6 GHz is determined. The potential total transmission rate of the array is several hundred Gbit/s.

Low threshold current and light output perpendicular to the wafer make vertical-cavity surface-emitting laser diodes (VCSELs) attractive sources for optical interconnects.1,2 More than that, two-dimensional VCSEL arrays for parallel data processing are potential candidates for optical computers. A modulation bandwidth of 6 GHz (Ref. 3) and highly efficient fiber coupling to multimode fibers4 of 10 × 10 VCSEL arrays has already been shown. Here we demonstrate, for the first time to our knowledge, transmission of 1-Gbit/s data rates in 4.5-μm-core-diameter single-mode fibers as elements of these arrays. The individual lasers show low feedback sensitivity, requiring a 1.5-dB power penalty for a - 10-dB feedback level at a bit error rate (BER) of 10−11.

We report on planar proton implanted vertical-cavity surface-emitting laser diodes (VCSELs) with high output powers and high wall plug efficiencies for top surface emission. For optimized mirror reflectivities and proper mode alignment with respect to the gain spectrum a maximum cw output power of 15.5 mW and power conversion efficencies of 17.6 % are achieved for not heat sinked devices.

Vertical-cavity surface-emitting lasers (VCSELs) emitting in the wavelength regime around 980 nm are of increasing interest for high-capacity, short-distance data-link systems.1 These lasers show very high coupling efficiencies into silica fibers with large alignment tolerances, and large-size independently addressable two-dimensional arrays are readily fabricated.2 Low threshold voltages and high wall-plug efficiencies of 16.5%4 and 21%3 have also been achieved. Recently we reported6 on the linewidth behavior of such planar devices with AlAs/GaAs Bragg reflectors. Here we show an improved laser structure with linewidths below 30 MHz, linewidth-power products of 2.7 MHz mW, and linewidth-enhancement factors of 2.6, which are to our knowledge the best values obtained for VCSELs operating at room temperature.

Efficient planar proton implanted InGaAs-GaAs MQW vertical-cavity surface-emitting laser diodes (VCSEL's) and 2-D arrays are fabricated using molecular beam epitaxy. and p-type Beryllium doping. Using single-step grading and modulation delta-doping in the p-type AlGaAs-GaAs Bragg reflectors top surface emitting devices with a maximum wall-plug efficiency of 17.6% and a threshold voltage of 1.8 V are demonstrated. Transverse mode behavior is well described in terms of Laguerre-Gaussian functions, Independently addressable 10x10 arrays of 12 mu m diameter VCSEL's exhibit electrical 3-dB modulation bandwidths up to 6 GHz. Light from the array is simultaneously launched into a 10x10 multimode fiber bundle with coupling efficiency above 70% applying a simple butt-coupling technique.