Coherent optical turns 5

Ciena's 40G WaveLogic 2 line card, 2008 (Ciena)By Bo Gowan – To fully appreciate the impact that coherent optical technology has had on the telecom industry, you need to understand the barriers that optical vendors ran into as they looked to develop the next step in transport past 10G – and that story begins back in the go-go days of the late 1990s.

A team of engineers at Nortel had spent many weeks putting the finishing touches on a new optical transport demo unveiled on the company’s booth at Telecom 99.  The demo was an industry-first – transmitting 80 Gbps of data over a single wavelength of light across a span of 480 kilometers from Geneva to Paris – and it caught the attention of the entire industry.

In 2001, the huge optical boom came to a crashing end. Network operators had drastically overbuilt global fiber capacity during the bubble, and it would be years before spending on optical transport equipment would fully rebound. The demands coming from network operators changed in an instant for optical equipment vendors.

With new network builds no longer on the horizon, Dino DiPerna and his team knew that a completely new direction was needed.

What the team produced was not so much of a single change in optical transmission but an entire series of new optical transport concepts and inventions that together enabled what we know today as coherent optical transport.

“That first chip was the birth of what we now call WaveLogic, it was the first generation of DSP-assisted electro-optics,” said DiPerna. “Transmit digital compensation allowed the use of a traditional receiver design without the need for the customer to worry about dispersion. We knew we were on a path that represented the future of optical transport.”

But to achieve coherent 40G required a revolutionary set of new technologies and innovations that could all fit together in perfect compliment.

“That 40G coherent project was a great example of a diverse team coming together to solve a problem from all angles,” said DiPerna. “Individually, each technology advancement was impressive – whether it be the advanced DSP, the coherent receiver using DP QPSK, the analog-to-digital converter development, or a dozen other parts to the puzzle.” more>



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