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Japanese Giant Builds Computer Memory With Light

• Eric Smalley via

A piece of the future internet has surfaced in a lab in Japan: a memory chip that stores bits of light.

Researchers at Japanese telecom giant NTT have built an optical random access memory (o-RAM) chip — a conceptual cousin to the electronic memory in your computer. The goal is not to make a light-speed replacement for DRAM. That’s out of the realm of possibilities for the foreseeable future. Rather, the idea is to make fast, efficient storage buffers for internet routers and the communications switches that connect thousands of servers in data centers.

The NTT researchers built a 4-bit prototype that operates at 40 gigabits per second. If the technology were scaled up, a 1 megabit device would take up a square centimeter and consume less than 100 milliwatts. “Our RAM is just a 4-bit memory. We need to increase the scale of integration,” says NTT researcher Masaya Notomi.

NTT is targeting 10-kilobit to 1-megabit memory chips for future all-optical routers. According to Notomi, the prototype shows that these goals are reasonable in terms of size and power consumption. Getting to that scale will take time. The company expects to reach 10 kilobits by around 2020, and 1 megabit by around 2025.

Optical RAM doesn’t have to hold very much to be useful for networking. Buffers on future optical routers could be very small compared to the electronic memory used today, says Nick McKeown, an electrical engineering and computer science professor at Stanford. McKeown calls a device that can hold 500 kilobits and read and write data at 100 gigabits per second “very interesting.”