An Van Hove

Development of a red VCSEL-to-plastic fiber module for use in parallel optical data links

This paper presents results that have emerged from the European funded ESPRIT Project, Bright Red Surface Emitting Lasers (BREDSELS-23455). The projects main objective has been to develop arrays of Vertical Cavity Surface Emitting Lasers (VCSELs) emitting in the region of 650 nm. These VCSEL arrays, suitably coupled to plastic fiber ribbon, are potentially ideal sources for high-speed plastic optical fiber networks. Linear 1 X 8 VCSEL arrays have been fabricated from wafers grown in multi-wafer MOVPE reactors. Individual VCSELs are shown to generate a peak room temperature power of 2 mW at 674 nm and are capable of operating continuous wave to a temperature of 60 degrees Celsius. The use of selective oxidation in the fabrication process is found to be essential in terms of providing effective heat sinking to the active region, while free carrier absorption is found to be a significant loss mechanism. A detailed description of the device results including modal behavior is presented along with the initial results from the plastic fiber ribbon module.

Microcavity LED-based parallel data link using small-diameter (125 m) plastic optical fibres

Parallel optical data links using high-efficiency microcavity LEDs (MCLEDs) and small-diameter plastic optical fibre ribbons are proposed. MCLED performance, coupling efficiencies, alignment tolerances, plastic optical fibre end-facet termination techniques and first link experiments are studied.

Microgroove fabrication with excimer laser ablation techniques for optical fiber array alignment purposes

Currently, an ever increasing need for bandwidth, compactness and efficiency characterizes the world of interconnect and data communication. This tendency has already led to serial links being gradually replaced by parallel optical interconnect solutions. However, as the maximum capacity for the latter will be reached in the near future, new approaches are required to meet demand. One possible option is to switch to 2D parallel implementations of fiber arrays. In this paper we present the fabrication of a 2D connector for coupling a 4x8 array of plastic optical fibers to RCLED or VCSEL arrays. The connector consists primarily of dedicated PMMA plates in which arrays of 8 precisely dimensioned grooves at a pitch of 250 micrometers are introduced. The trenches are each 127 micrometers deep and their width is optimized to allow fixation of plastic optical fibers. We used excimer laser ablation for prototype fabrication of these alignment microstructures. In a later stage, the plates can be replicated using standard molding techniques. The laser ablation technique is extremely well suited for rapid prototyping and proves to be a versatile process yielding high accuracy dimensioning and repeatability of features in a wide diversity of materials. The dependency of the performance in terms of quality of the trenches (bottom roughness) and wall angle on various parameters (wavelength, energy density, pulse frequency and substrate material) is discussed. The fabricated polymer sheets with grooves are used to hold optical fibers by means of a UV-curable adhesive. In a final phase, the plates are stacked and glued in order to realize the 2D-connector of plastic optical fibers for short distance optical interconnects.

MT compatible red VCSEL module for parallel optical interconnections

In this paper we present the design, fabrication and characterization of a module which directly connectorizes a 1 by 8 red VCSEL array to a small diameter polymer optical fiber array, using a standard MT ferrule. The facets of the POF are prepared by a hot knife cutting, followed by a short polishing step. First coupling results show total losses in the range of 1.1 dB/channel for a 30 cm POF link. Optical crosstalk between adjacent channels is below -45 dB. Plastic micromachined parts surrounding the VCSEL chip ensure the correct alignment of the connector, using the connector, using the connector guiding points. The parts themselves are aligned to the chip with a n index-alignment technique, using an excimer laser ablated mastertool. In a deconnectorizable version of the module, a thin, flat glue layer on the chip acts as a window between the VCSEL chip and the MT terminated POF array. Integrated in a standard ceramic package, clear eye diagrams have been measured at 150 MHz for a 10m POF link, coupled to the VCSEL array. Further efforts on higher speed measurements using dedicated drivers, will also be presented.

Realisation of highly efficient and high-speed Resonant Cavity LED for coupling to Plastic Optical Fibres

Planar Resonant Cavity LEDs (RCLEDs) are suitable light sources for parallel interchip interconnect links, due to their high efficiency, zero-threshold, low voltage, high reliability and high speed characteristics. The through- substrate emitting RCLEDs, optimized for Polymer Optical Fiber (POF) coupling, consist of an InGaAs quantum sandwiched between a metal mirror and a distributed Bragg reflector. The RCLEDs are arranged in 8 X 8 arrays with 250 um pitch. The arrays have been mounted onto glass carriers, and the coupling efficiency into POF, the far- field pattern and the modulation characteristics are measured. The overall quantum efficiency of the devices with 50 um diameter was found to be 13.4%, the QE into POF was 3.7%. The large-signal transient behavior of the devices has been investigated. Using a high-speed pulse source, nanosecond rise and fall times have been measured. Wide open eye diagrams at 1 Gbit/s were obtained using voltage pulse drivers. These data were compared to theoretical results based on a non-linear rate equations model.

Microcavity LED-based parallel data link using small-diameter (125-μm) plastic optical fibers

Parallel optical data links using high efficiency Microcavity LEDs and small diameter POF ribbons are proposed. MCLED performance, coupling efficiencies, alignment tolerances, POF end facet termination techniques and first link experiments are studied.