ClariPhy samples 40G coherent chip

SAN JOSE, Calif. – Startup ClariPhy is sampling a single CMOS chip aimed at lowering the cost of upgrading long distance optical networks to 40 Gbits/second. The chip is part of a rising tide of silicon for next-generation carrier and data center networks at 40 and 100 Gbit/s data rates.

Carriers are coming to agreement that the next-big step for their long haul networks is 40G transport using dual-polarization QPSK, a coherent form of optical modulation, said ClariPhy founder and chief technology officer Norm Swenson. Standards have been set for DP-QPSK at both 40 and 100G nets, he said.

"There have been many attempts at how to handle [optical long haul upgrades], but now people have gelled on this approach," said Swenson.

The coherent technology "treats light like a radio wave, making use of phase and amplitude information," said Swenson. Designers can use the phase information—lost in today's direct detection technology—to handle several forms of optical signal dispersion in a single CMOS DSP.

Current systems based on direct detection of the light signal use additional components, sometimes requiring additional line cards, to improve the quality of optical signals sent over long distances. The coherent technique also can improve signal sensitivity by using a local oscillator, Swenson said.

ClariPhy has been working for two years on its 40nm chip which is now integrated in customer systems, some of which may already be used in carrier tests. The chip dissipates about 16W and is based on the company's own internally developed analog-digital converter and DSP technology.

The startup hired a signal processing expert early on who created a DSP lab in Argentina. It has analog expertise at its headquarters in Irvine, Calif.

"I worked on a coherent system 10 years ago, but it was all discrete components," said Swenson. "Now you can design a single chip that can do this if you have a very good analog-to-digital front end," he said.

The ClariPhy chip will be in production this fall. At least one other company is expected to debut a 40G coherent chip soon.