OpVista's DMC modulation could speed 40G deployments

OpVista announced a new modulation format called DMC (Dense Multi-Carrier) in an effort to boost system capacity and grab a piece of the emerging 40G/100G market. OpVista's DMC technology looks promising: it uses standard 10G components to fit a 40G signal in the same space as a 10G signal on existing systems, and does not require expensive dispersion compensation techniques or complete system rebuilds. OpVista plans to offer the technology on its own optical networking equipment and also as a stand-alone transponder for use as alien wavelengths on competitors' 10G transport systems.

DMC is similar to OpVista's Ultra DWDM branded multi-carrier technology, which uses four 2.5G carriers to create a 10G optical signal. The difference is that DMC combines four 10G carriers inside the same window, effectively quadrupling bandwidth without increasing the symbol rate. Thus the modulated 40G signal behaves like a 10G signal and is compatible with existing DWDM network components, such as mux/demux filters and reconfigurable add-drop multiplexers (ROADMs).

This is a huge benefit because operators do not have to reengineer systems or deploy additional dispersion compensation, either or both of which creates a significant economic barrier for many 40G implementations.

One impediment to 40G deployments is the high cost of components and high risk of supply disruption due to the small number of manufacturers in the supply chain. OpVista claims DMC uses standard 10G components that are widely available from multiple sources at a much lower cost. Being able to manufacture 40G line cards with off-the-shelf 10G components gives OpVista a huge edge versus other vendors in that it can offer 40G functionality at a reduced cost.

DMC is similar in concept to Nortel's DP-QPSK, but while Nortel's solution depends on innovative, internally developed components, OpVista combines standard 10G components with analogue and digital design in a novel way. Nortel's DP-QPSK modulation scheme has the best spectral efficiency, best tolerance to dispersion, and greatest reach, but DMC specifications exceed all other modulation schemes on the market and are acceptable for most network applications. 

Furthermore, because a 40G signal modulated using DMC behaves like a normal 10G signal, OpVista can address metro, regional, ULH and even sub-sea applications with the same technology. OpVista plans to offer a DMC-based 40G transponder option that will allow operators to overlay 40G on their existing networks using alien wavelengths; it has been running a number of trials testing various applications. 

DMC could change the 40G/100G game

40G has been slow to take off due to the current price premium of 40G transponders compared to four 10G transponders and the high costs associated with adding more dispersion compensators. Deployments to date have targeted mostly router interconnect applications augmented by a few capacity exhaust scenarios "” and a lot of trials.

Given the increasing demand for bandwidth on operator networks needed to accommodate video and high speed data applications, most large carriers are looking for cost effective methods to increase capacity on their networks. If OpVista's DMC operates and is as cost effective as advertised, it could lower costs and increase adoption rates for 40G much quicker than we have predicted.

OpVista's willingness to provide its technology as an external transponder is a smart move. Currently OpVista is a niche metro WDM vendor, and although it has a good base of customers, it stands to gain a lot more by providing the external transponder solution.

OpVista appears to be in the right place with the right technology at the right time "” not a bad place to be.

Ron Kline, Research Director

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