G. C. Boisset

Design and construction of an active alignment demonstrator for a free-space optical interconnect

An x-y active alignment system based on Risley beam steerers is described. The demonstrator features a quadrant detector which detects the misalignment error between the center of a spot of light and the center of the quadrant detector. This misalignment error is then used by a new algorithm to calculate the rotational displacement required for the two Risley beam steerers to steer the spot of light to the center of the quadrant detector. The experimental results indicate that any spot misaligned by up to 160 /spl mu/m on the quadrant detector will be systematically centered by the demonstrator system.<<ETX>>

Design, implementation, and characterization of a hybrid optical interconnect for a four-stage free-space optical backplane demonstrator

A four-stage unidirectional ring free-space optical interconnect system was designed, analyzed, implemented, and characterized. The optical system was used within a complementary metal-oxide semiconductor-self-electro-optic-effect-device-based optical backplane demonstrator that was designed to fit into a standard VME chassis. This optical interconnect was a hybrid microlens-macrolens system, in which the microlens relays were arranged in a maximum lens-to-waist configuration to route the optical beams from the optical power supply to the transceiver arrays, while the macrolens optical relays were arranged in a telecentric configuration to route optical signal beams from stage to stage. The following aspects of the optical system design are discussed: the optical parameters for the hybrid optical system, the image mapping of the two-dimensional array of optical beams from stage to stage, the alignment tolerance of the hybrid relay system, and the power budget of the overall optical interconnect. The implementation of the optical system, including the characterization of optical components, subsystem prealignment, and final system assembly, is presented. The two-dimensional array of beams for the stage-to-stage interconnect was adjusted with a rotational error of <0.05 degrees and a lateral offset error of <3.5 mum. The measured throughput is in good agreement with the lower-bound predictions obtained in the theoretical results, with an optical power throughput of -20.2 dB from the fiber input of the optical power supply to the modulator array and -25.5 dB from the fiber input to the detector plane.

An optical backplane demonstrator system based on FET-SEED smart pixel arrays and diffractive lenslet arrays

We have demonstrated a representative portion of an optical backplane using FET-SEED smart pixels and free-space optics to interconnect printed circuit boards (PCBs) in a two board, unidirectional link configuration. 4/spl times/4 arrays of FET-SEED transceivers were designed, fabricated, and packaged all the PCB level, The optical interconnection was constructed using diffractive microoptics, and custom optomechanics. The system was operated in two modes, one showing high data throughput, 100 MBit/sec, and the other demonstrating large connection densities, 2222 channel/cm/sup 2/.<<ETX>>

On-die diffractive alignment structures for packaging of microlens arrays with 2-D optoelectronic device arrays

A novel technique for aligning a microlens array to an electrically packaged optoelectronic device array is presented: reflective Fresnel zone plates (FZPs) are fabricated on the device die to provide registration spots during alignment. A proof-of-concept experiment in which an MSM array was aligned to a microlens array with an accuracy of better than 9 microns is described.

4x4 Vertical-Cavity-Surface- Emitting Laser (VCSEL) and Metal-Semiconductor-Metal (MSM) Optical Backplane Demonstrator System

We describe a system demonstrator based on vertical-cavity surface-emitting lasers, metal-semiconductor-metal detectors, printed circuit board (PCB) level optoelectronic device packaging, a compact bulk optical relay, and novel barrel/PCB optomechanics. The entire system was constructed in a standard VME electrical backplane chassis and was capable of operating at >1.7 Gbit/s of aggregate data capacity. In addition to the component technologies developed, we describe operational testing and characterization of the demonstrator.

Optical, optomechanical, and optoelectronic design and operational testing of a multi-stage optical backplane demonstration system

In this paper, we describe the optical, optomechanical, and optoelectronic design of a multistage optical backplane demonstration system. In addition, operational testing and performance is discussed.

Optomechanics for a four-stage hybrid-self-electro-optic-device-based free-space optical backplane

We present the design, fabrication, and testing of optomechanics for a free-space optical backplane mounted in a standard 6U VME backplane chassis. The optomechanics implement an optical interconnect consisting of lenslet-to-lenslet, as well as conventional lens-to-lens, links. Mechanical, optical, electrical, thermal, material, and fabrication constraints are studied. Design trade-offs that affect system scalability and ease of assembly are put forward and analyzed. Novel mounting techniques such as a thermal-loaded interference-fitted lens-mounting technique are presented and discussed. Diagnostic tools are developed to quantify the performance of the optomechanics, and experimental results are given and analyzed.

Design, implementation, and characterization of an optical power supply spot-array generator for a four-stage free-space optical backplane.

The design and implementation of a robust, scalable, and modular optical power supply spot-array generator for a modulator-based free-space optical backplane demonstrator is presented. Four arrays of 8 x 4 spots with 6.47-mum radii (at 1/e(2) points) pitched at 125 mum in the vertical direction and 250 mum in the horizontal were required to provide the light for the optical interconnect. Tight system tolerances demanded careful optical design, robust optomechanics, and effective alignment techniques. Issues such as spot-array generation, polarization, power efficiency, and power uniformity are discussed. Characterization results are presented.

Packaging of two-dimensional smart pixel arrays

The optomechanical and electronic packaging of two-dimensional smart pixel arrays present a series of constraints that complicate the application of standard electrical packaging approaches in system applications. Through the construction of demonstrator systems, we have designed, fabricated, and implemented smart pixel packaging which uniquely addresses the critical issues associated with successfully integrating two-dimensional optoelectronic device arrays into systems. In order to take full advantage of this class of optoelectronics, aggressive packaging solutions which use both existing and new microelectronic packaging technologies have been employed. Key system design considerations such as electrical bandwidth and connectivity, thermal management, and optical alignability have played a role in the choice of packaging solution. In this paper, we will describe smart pixel packaging designed, modelled, fabricated and demonstrated for board-to-board optical interconnect applications.

In situ measurement of misalignment errors in free-space optical interconnects

A nonobtrusive technique for measuring misalignment errors in multistage free-space optical interconnects is proposed. The technique makes use of dedicated microoptics to relay higher order dedicated alignment beams generated by an optical power supply onto alignment detectors located on the periphery of a smart pixel chip. An implementation of this technique for measuring lateral (x-y) misalignment error in a multistage optical backplane demonstrator is then presented. Performance parameters are analyzed and future directions such as photonic extensions to electronic boundary scan standards are suggested.