IBM drills optical vias in chip for 1Tbit/sec transmission

March 9, 2012 — IBM (NYSE:IBM) scientists developed a prototype optical chipset, Holey Optochip, that can transfer 1 trillion bits (1Tbit) per second as a parallel optical transceiver, or 8X faster than today’s parallel optical components. IBM expects to commercialize the concept within a decade, with the help of its chip manufacturing partners.

The chip-scale transceiver relies on higher levels of integration, power efficiency and performance through packaging and circuit innovations, said IBM Researcher Clint Schow, part of the team that built the prototype. Optical chips transfer data using light pulses instead of electron transmission on wires. The aim is to use optical signals on chips made via standard low-cost/high-volume manufacturing methods.

Photo 1. IBM’s Holey Optochip. Original chip dimensions are 5.2 x 5.8mm.

To make the Holey Optochip, IBM fabricated 48 through-silicon holes (optical vias) through a standard 90nm silicon CMOS IC. The holes allow optical access through the back of the chip to 24 receiver and 24 transmitter channels, creating an ultra-compact, high-performing and power-efficient optical module. The transceiver consumes <5W power. The Holey Optochip module is constructed with components that are commercially available today, with an eye on future commercial scaleability.

Simple post-processing on completed CMOS wafers with all devices and standard wiring levels results in an entire wafer populated with Holey Optochips. The transceiver chip measures 5.2 x 5.8mm. Twenty-four channel, industry-standard 850-nm VCSEL (vertical cavity surface emitting laser) and photodiode arrays are directly flip-chip soldered to the Optochip. This direct packaging produces high-performance, chip-scale optical engines.

The Holey Optochips are designed for direct coupling to a standard 48-channel multimode fiber array through an efficient microlens optical system that can be assembled with conventional high-volume packaging tools.

Photo 2. The back of the IBM Holey Optochip with lasers and photodectors visible through substrate holes. 

Parallel optics is a fiber optic technology primarily targeted for high-data, short-reach multimode fiber systems that are typically less than 150m. Parallel optics differs from traditional duplex fiber optic serial communication in that data is simultaneously transmitted and received over multiple optical fibers.

The research will be presented at the Optical Fiber Communication Conference taking place in Los Angeles. Learn more at

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