05 Dec 2002
NTT, the Japanese telecom giant, has broken the speed limit for electronics.
Scientists at NTT's laboratories in Japan claim to have made an integrated circuit (IC) for optical communications that can process 100 Gbit/s data streams -- ten times the speed of existing network chips.
Details of the breakthrough will be presented in a post-deadline paper at the annual International Electron Devices Meeting (IEDM) in San Francisco, next week.
Researchers from the firm's Photonics Laboratories used indium phosphide (InP) to fabricate a multiplexer chip that combines lower data rate signals into a single 100 Gbit/s stream. The team also made a demultiplexer that performs the reverse function.
Today, installed optical networks operate with a channel speed of 10 Gbit/s with next generation 40 Gbit/s systems expected to roll out within the next couple of years. However, scientists have struggled to make electronics that reliably operate at significantly faster speeds.
NTT says that two developments allowed it to make 100 Gbit/s chips. The first was perfecting crystal growth methods that enable reproducible fabrication of high quality transistors that have gate lengths of just 100;;nm and a cut-off frequency of around 200 GHz. The second was a new circuit design that does not have a conventional output buffer.
A spokesman from NTT told Optics.org that the InP technology may operate even faster and have an ultimate speed limit beyond 160 Gbit/s. To put this into context, NTT says that a complete 100 Gbit/s communication system would be able to transmit all the data on a 6 hour video or 3 DVDs in approximately 1 s.
However, before systems can become a commercial reality, much work is still needed. For example, scientists still need to develop technologies for packaging the chips and to build a 100 Gbit/s optical modulator for encoding data at the transmitter.
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.