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8 December 2011
 
Alcatel-Lucent has enhanced the optical performance of its 100G single-carrier coherent technology. The company's 100Gbps extended reach (100G XR) line card, used with its 1830 Photonic Service Switch, improves performance by 30% by fine-tuning the algorithm that runs on its coherent receiver ASIC. The system vendor says the typical optical reach now extends to 2,000km.
 
When Alcatel-Lucent first announced its 100Gbps technology in June 2010, it claimed a reach of between 1,500 and 2,000km. With the 100G XR, this upper reach is now met for most networking scenarios.
 
"By announcing the extended reach, Alcatel-Lucent is able to highlight the 2,000km reach as well as draw attention to the fact that it has many deployments already, and that some of those customers are using 100 gig in 1,000km-plus applications," said Sterling Perrin, senior analyst at Heavy Reading.
 
The line card's improved optical performance equates to transmission across longer fibre spans before optical regeneration is required. This saves equipment cost, power and space. It also means more complex network topologies can be implemented such as mesh networks where the signal encounters varying length paths based on differing fibre types, as well as multiple reconfigurable optical add-drop multiplexer (ROADM) stages.
 
Alcatel-Lucent says it has implemented a 1,700km link comprising 20 amplifiers and seven ROADM stages, removing the optical regeneration.
 
To improve the optical performance on the 100G XR, Alcatel-Lucent has not amended the hardware. Instead it has tweaked the dispersion compensation algorithm that runs on the DSP, making use of experience Alcatel-Lucent has gained from existing 100Gbps deployments.
 
"We can tune various parameters, such as power and the way it [the algorithm] deals with impairments," said Sam Bucci, vice president, terrestrial portfolio management at Alcatel-Lucent. This includes increased tolerance to polarization mode dispersion and non-linear impairments.
 
The 100G XR card is being tested by customers and is generally available from December 2011.
 
By Roy Rubenstein