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4 October 2011
MultiPhy has detailed its 100Gbps direct-detection receiver IC addressing the metro market. The MP1100Q IC is targeting two applications: a point-to-point module to connect data centers with a reach of up to 80km, and a DWDM design for metro, core and regional networks with a reach up to 800km.
The M1100Q uses a 4x28Gbps direct-detection design. This is similar to the approach announced by ADVA Optical Networking recently for its 100Gbps metro card.  But MultiPhy claims that the 100Gbps DWDM CFP module will squeeze the four bands that make up the 100Gbps signal into a 100GHz-wide channel rather than 200GHz, while its chip implements the maximum likelihood sequence estimation (MLSE) algorithm to achieve the 800km reach.
The four optical channels received by a CFP module are converted to electrical signals using four receiver optical subassemblies (ROSAs) and sampled using the MP1100Q’s four analogue-to-digital converters operating at 28Gbps. The CFP design using MultiPhy’s chip needs only use 10Gbps optoelectronics for the transmit and receive paths. The result is a 100Gbps module with a cost structure based on 10Gbps optics.
The lower bill-of-materials impacts performance, however. “When you over-drive these 10Gbps optoelectronics – on the transmit and the receive side – you create what is called intersymbol interference," said Neal Neslusan, vice-president of sales and marketing at MultiPhy.
Intersymbol interference is an unwanted effect where the energy of a transmitted bit leaks into neighbouring signals. This increases the bit-error rate and makes the detector's task more difficult. "The way that we get around it is using MLSE, recognised as the best solution for mitigating inter-symbol interference," said Neslusan.
Unwanted channel effects introduced by the fibre, like chromatic dispersion, also induce intersymbol interference and are also countered by the MLSE algorithm on the MP1100Q.
First chip samples will be with customers in the fourth quarter of this year, with general availability starting in early 2012.
By Roy Rubenstein