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We are developing a 1x8 single mode (SM) optical interface to facilitate the adoption of dense wavelength division multiplexing (DWDM) silicon photonic (SiPh) optical interconnects in exascale computing systems. A common method for fiber attachment to SiPh transceivers is ‘pigtailing’- the permanent adhesive bonding of fiber/v-groove arrays to onchip grating couplers (GC). This approach precludes standard high throughput surface mounting and solder reflow assembly of the transceiver onto system printed circuit boards. Our approach replaces the fixed pigtail with a low profile, small form factor, detachable expanded beam optical connector which consists of four essential parts: a GC array, a surface mount glass microlens array chip, an injection molded solder reflowable optical socket, and an injection molded SM light turn ferrule. The optical socket and ferrule are supplied by US Conec Ltd. To design the GC, we developed an optical simulator that considers CMOS foundry constraints in the optimization process. On-wafer measurements of the GC coupling loss to SMF28 fiber at 1310nm is ~1.4dB with a 1dB bandwidth of ~22nm. This ensures a wide low loss spectral window for at least 16 DWDM channels. The geometry of the optical system is arranged so that only a simple spherical lens is required for efficient mode matching in the expanded beam space. The fiber to fiber insertion loss through the light turn ferrule, two microlenses and GCs, and a looped back SOI waveguide ranged from 4.1-6.3dB, with insertion loss repeatability of 0.2dB after multiple mating cycles.

An expanded beam optical interconnect is introduced that provides a separable connection between photonic integrated circuit and single-mode fiber. Insertion loss data are provided and stability through solder reflow is demonstrated.

As parallel optics data rates transition from 10 Gbps to 25 Gbps and beyond, VCSELs and photodiodes (PDs) are evolving to support the higher transmission rates. In order to maintain system performance as speeds increase and tolerances become tighter, an improved method is needed to efficiently couple VCSEL/PD array optical outputs to fiber optic networks. The mechanical-optical interface (MOI) is a monolithic component with an array of collimating lenses designed for efficient coupling between the on-board active components and a detachable fiber optic connector. This paper describes the design and implementation of a next generation MOI to match high speed VCSEL/PD requirements. Improvements to an earlier design were made to accommodate a wider variety of transceiver architectures by taking into account chip driver and wire-bond clearance requirements, while also optimizing the optical design to maximize coupling performance. Monte Carlo simulation results and the sensitivity analysis used to optimize optical performance with respect to VCSEL/PD alignment and coupling requirements are presented. Empirical testing results are shown to validate the optical model and subsequent system performance; eye-diagram results of a 25 Gbps error-free link are provided across a broad operating temperature range. Environmental and mechanical testing of the component after alignment and adhesion to the circuit substrate validates part and epoxy interaction and performance.