SoC targets 40 Gbit/s coherent optical networks

May 24, 2011 // By Phil Ling
The move from10 Gbit/s to 40 Gbit/s optical networks is driving demand for adoption of coherent technology, overcoming the reach limitations of the incumbent direct detect solutions which require a greater number of repeaters. Moving to coherent technology is expected to lower the cost of offering 40 Gbit/s significantly, enabling operators to roll out higher bandwidth to their customers.

According to PMC Sierra, the industry must move to coherent technology in order to meet the commercial parameters of offering 40 Gbit/s. It hopes to meet the resulting demand with its POLO family of 40 Gbit/s coherent solutions for metro, regional and long-haul networks.

According to the company, the POLO architecture doubles line card density and reduces power consumption by more than 50 percent when compared to 40 Gbit/s non-coherent network deployments.

Non-coherent networks suffer much more from dispersion artifacts at 40 Gbit/s than 10 Gbit/s and while there are mitigating technologies in place to solve this, they increase the cost of network deployment.

Coherent technology is said to overcome these issues and remove the need for expensive optical compensation solutions, which aren’t able to scale to 40 Gbit/s.

Trials of 40 Gbit/s coherent technologies have been carried out for the last three years and system-level solutions are still only in development.

PMC Sierra believes its POLO technology could short-circuit further trials and development by delivering a chip-level solution than can scale.

The company also claims that in its own trials it has achieved a 25 percent increase in reach over competing coherent solutions at 40 Gbit/s.

This is the company’s first product launch in the 40 Gbit/s coherent space but believes the move to this technology will now be rapid. AT&T and Veriozon are expected to cease deployment of non-coherent 40 Gbit/s shortly.

It also believes that operators moving to 40 Gbit/s coherent technology will be able to gain market share over the incumbent operators slower to adopt the next-generation higher bandwidth solution. One of the main problems with non-coherent technology as they move beyond 10 Gbit/s is their reach; at 10 Gbit/s a span may be up to 80 km but at 40 Gbit/s this drops by a factor of 16. Coherent technology makes use of both amplitude and phase of the signal, to put more data in