Electro-optical Circuit Board Research Articles

Variable Launch System for the Metrology of EOCBs

Optical links within data centres are critical components supporting increasing data consumption. These links vary in technologies, and metrological standards for the industry are still being developed. Concerning specific multimode interconnects for high data rates, we present the use of a system incorporating a variable controlled launch condition as a platform for characterizing the effect of temperature on electro-optical circuit boards (EOCBs) for metrology.

Electronic‐photonic board as an integration platform for Tb/s multi‐chip optical communication

Chip-on-board silicon photonics O-band wavelength-division multiplexing transceivers have been developed that will eventually enable high-throughput on-board optical communication for multi-socket on-board communication. This direct, any-to-any configuration yields low-latency, low-power optical communication among multiple compute nodes on the board. Silicon photonic transceiver chips are flip-chipped on a polymer waveguide containing an electro-optical circuit board using adiabatic coupling and then completed with driver and amplifier electronic chips. A transceiver assembly based on wire-bond technology verifies 50 Gb/s operation per channel, and the flip-chip version demonstrates the chip on-board assembly techniques for compact on-board transceivers.

Characteristics and crosstalk of optical waveguides fabricated in polymethyl methacrylate polymer circuit board.

Electro-optical circuit boards should provide simple and cost-effective coupling techniques and crosstalk levels of less than -30 dB. A dicing saw was used to create waveguide grooves with a surface roughness of less than 183 nm in a 1.6-mm-thick polymethyl methacrylate polymer (PMMA) substrate. The buried optical waveguides were made from SU-8 in a PMMA substrate covered with a 1-mm PMMA sheet. The propagation loss for a 500 μm×570 μm straight waveguide was 0.9 dB/cm at 1310 nm. The coupling between parallel waveguides was measured at separation distances from 45 to 595 μm. The crosstalk was less than -40 dB for 65-mm-long waveguides. This fabrication method shows potential for dense optical interconnects with very low crosstalk.

Large Optical Backplane With Embedded Graded-Index Glass Waveguides and Fiber-Flex Termination

Introduction of electro-optical circuit board (EOCB) technologies based on embedded glass waveguides in the system enclosure of current data storage, compute, or switch platforms will be instrumental in accommodating the prohibitive bandwidth densities projected in exascale data centers, access networks, and high-performance computing environments in future. The main focus of this paper is, therefore, on the realization of large EOCB backplanes (350 × 465) mm2 with passive dual-star interconnect topologies. The waveguides are embedded inside glass panels using a two-step thermal ion exchange process [1] . The fabricated embedded waveguides are then characterized for propagation and coupling losses across different wavelength ranges and for different coupling arrangements. The fabrication process for these large panels is briefly explained accompanied by the lamination process of four separate glass panels. The connectivity between backplane and peripheral cards is addressed using fiber flex termination with two possible waveguide interfaces—actively assembled pluggable interface and passively assembled adhesive bonded interface. A demonstration platform is also finally reported and the viability evaluated for optical connectivity and system efficiency is tested for the whole system containing fiber flex termination.

Display glass for low-loss and high-density optical interconnects in electro-optical circuit boards with eight optical layers.

Parallel optical interconnects on-board level requires low propagation loss in wavelength range between 850 and 1550 nm to be compatible with datacom and telecom optical engines. For highest integration density tight waveguide bends and a scalable number of optical layers should be manufacturable for 2D interfaces to optical fiber array connectors and photonic assembly I/O's. We developed a glass waveguide panel process for double-sided processing of commercial available display glass by applying a two-step thermal ion-exchange process for low-loss multi-mode graded-index waveguides. Multiple glass waveguide panels can be embedded between electrical layers. The generic concept enables fabrication of high-density integration (HDI) electro-optical circuit boards (EOCB) with high number of optical and electrical layers. Waveguides with high NA of 0.3 for low bend losses could be achieved in glass with propagation loss of 0.05 dB/cm for all key wavelengths. Four of those glass waveguide panels were embedded in an EOCB demonstrator with size of 280 x 233 mm² providing eight optical layers with 96 channels in an area of 2.8 x 1.5 mm². To the best of our knowledge it's the highest number of layers that has ever been demonstrated for an EOCB.

Pluggable Electro-Optical Circuit Board Interconnect Based on Embedded Graded-Index Planar Glass Waveguides

Widespread adoption of electro-optical circuit boards based on embedded glass waveguide technology would enable seamless optical connectivity from external fiber-optic networks to system embedded optical interconnect architectures. In this paper, we report on the fabrication of planar multimode waveguides within thin glass foils based on a two-step thermal ion exchange process. Novel lamination techniques were developed to allow glass waveguide panels to be reliably integrated into a conventional electronic multilayer printed circuit board. In addition, a complete suite of optical connector technologies were developed to enable both direct fiber-to-board and board-to-board connectivity. We present the design, development, and characterization of a fully integrated connection platform, comprising a $281 \times 233$ mm2 multilayer electro-optical backplane with integrated planar glass waveguides, a pluggable connector system, and five pluggable test cards. Both on-card and externally generated 850 and 1310-nm optical test data were conveyed through the connector and waveguide system and characterised for in-system and system-to-system optical connectivity at data rates up to 32 Gb/s per channel exhibiting bit error rates of less than $10^{-12}$ .