IBM Breakthrough in Silicon Phototonic Technology

IBM silicon photonics

IBM have reached a major milestone in their development of silicon nanophotonic technology – announcing the production and testing of a first of its type, fully integrated photonic chip (IBM’s new CMOS Integrated Nano-Photonics Technology).

Silicon photonic technologies combine silicon-based chip engineering with optical components to transfer data via pulses of light. These pulses, created using lasers, perform the function of electrical signals sent through copper wires in today’s computer chips but have a host of added advantages.

Just as fiber optics revolutionized the telecommunications industry by speeding up the flow of data … this technology is designed to make future computing systems faster and more energy efficient

Arvind Krishna, senior vice president and director of IBM Research

Photonics allow for ultra fast data transfer – far faster than sending electrical signals down a wire. IBM’s latest tests demonstrated 25Gb/s per optical channel over a 2km transmitter-to-receiver distance.

For comparison, conventional PCI-E data cables (the standard industry technology for connecting peripheral devices) carry data at up to 8 Gb/s, while networking cables reach 40 Gb/s. The latest version of the USB standard tops out at 5Gb/s.

In just one second, this new transceiver is estimated to be capable of digitally sharing 63 million tweets or six million images, or downloading an entire high-definition digital movie in just two seconds.

Besides high-speed, IBM tests demonstrated excellent bandwidth performance whilst minimising problems typically encountered when using electrical signals to transfer over long distances. Notably, using photons instead of electrons results in minimal signal loss and minimised power usage.

The high calibre bandwidth properties of photonics are suited to small scale operations, for example chip-to-chip and board-to-board communications too. But these features are predicted to have especially significant consequences for cloud computing and handling of Big Data, which often requires shifting large volumes of data quickly between distant servers and computer systems.

View of a CMOS nanophotonic chip with multi-channel transceivers consisted of tightly integrated electrical and nanophotoncis circuits. An image of a finished 200mm wafer with CMOS Nanophotoncis circuits is overlaid on the background. Image rights: IBM.

The device is described as a wavelength-multiplexed chip because it’s capable of transmitting data over multiple wavelengths of light. Multiplexing devices allow for feeding several parallel optical data streams into a single fibre and is key to the high bandwidth performance of photonic chips.

The new chip uses four colours of light to transmit data over four independent optical channels. Since each channel supports a 25Gb/s data stream, in aggregate the chip is capable of supporting a bandwidth of 100Gb/s. As multiplexing is a scalable technology, IBM envision the technology to provide the basis for even larger, terabyte-scale data streams in future computer systems.


Nano Scale Integration

A key accomplishment of the announcement was IBM’s success at integrating multiple nanophotonic components (including wavelength multiplexers, modulators and photodetectors) alongside CMOS (Complementary Metal-Oxide Semiconductor) electrical circuitry on a single silicon chip.

Angled view of a portion of an IBM chip showing blue optical waveguides transmitting high-speed optical signals and yellow copper wires carrying high-speed electrical signals. IBM Silicon Nanophotonics technology is capable of integrating optical and electrical circuits side-by-side on the same chip.
A portion of an IBM chip showing blue optical waveguides transmitting high-speed optical signals and yellow copper wires carrying high-speed electrical signals. IBM Silicon Nanophotonics technology is capable of integrating optical and electrical circuits side-by-side on the same chip. Image rights: IBM.

Integrating nanophotonic components onto silicon chips (creating hybrid optical/photonic-electronic integrated circuits) has been a challenging process. In particular because of the thermal properties of the materials required in chip assembly. One obstacle was finding a way to bond optical chips onto silicon whilst avoiding fracturing of the solder used to secure components in place. Such hybrid devices are sought after however as they present the most practical, and viable short-term applications for photonic technologies.

Photonic-CMOS integration is important because the latter is the basic architecture of virtually all chips in use today. Using photonics for data transfer is great, but the bulk of computer operations are rooted in electronic processing of data. This means that hybrid photonic-electronic chips are required for current practical applications.

Within IBM’s photonic chip digital data is converted to an analog data stream that modulates a laser, sending an optical signal into a fibre. On the receiving end, light from the fibre is directed into a matrix of photo detectors that first convert the optical signal into an analogue one before digitising it for further use in traditional electric components.

In the longer term, it may be possible to construct wholly photonic-based computer systems. This would be advantageous, since multiple conversions back and forth between optical and electrical signals is inherently inefficient (requiring dedicated components and additional energy). But such a fully optical system is a way off for the time being.

It’s also significant that the new chip can be manufactured using existing chip assembly practices. This should hasten its emergence into commercial markets in the very near future – but an exact date hasn’t been confirmed by IBM. The press announcement from IBM only stated the recent accomplishments “will soon enable manufacturing of 100 Gb/s optical transceivers”.


Big Data Applications

The new chip has been developed under IBM’s CMOS Integrated Nano-Photonics Technology research program. Its work is geared toward the company’s efforts and $3 billion investment to push the limits of chip technology to meet the emerging demands of cloud computing and Big Data systems. More specifically, there’s urgent need for technologies that can send, analyse and handle high volumes of data at high speed.

Silicon photonics will be a fundamental technology to address the bandwidth, latency, and energy challenges in the fabric of high-end systems. (IEEE)

Image rights: German Climate Computing Center
Photonic-based chips hold massive promise for increasing speed and efficiencies of information transfer in servers, and between data centers. Image rights: German Climate Computing Centre.

With the Internet of Things (IoT) just around the corner and cloud computing expanding at pace we’re seeing the emergence of what some are terming the ‘Big Data scenario’. A information landscape with processing requirements so large and complex that efficient processing is very difficult, and in places outright infeasible, using existing database-management tools and data-processing techniques.

Photonic computing fits neatly into this landscape on account of its capability to manage processing demands of Big Data. Of course photonics won’t be alone in answering the call for solutions. There are several core technologies under development that add important tools to a new arsenal for handling the data demands of tomorrow.

Considering the appeal of photonic computing, it’s of little surprise that IBM are not alone in developing the technology. Electronics companies such as Fujitsu, Intel, and NTT are also researching silicon photonics.



IBM Press Release

IBM Silicon Integrated Nanophotonics Research