WaveSplitter Gets Dynamic Over DWDM
Now it looks as though WaveSplitter was right all along. Its projects with Infineon Technologies AG (NYSE/Frankfurt: IFX) and Gemfire Corp. are pushing the envelope on integrating electronic and optical devices in compact modules (see Infineon, WaveSplitter Demo Monitor and WaveSplitter, Gemfire Demo VOA Mux).
WaveSplitter is targeting the same goal as many of its competitors -- adding ways of monitoring and adjusting light power to the mux/demux modules used in DWDM systems -- but it's going about it in a different way. Rather than tackling the whole project itself, it's partnering with companies with established expertise in these technologies.
Wavesplitter itself reckons it's got some pretty cool (low insertion loss) Arrayed Waveguide Gratings (AWGs), one of the main technologies for making mux/demux components. Infineon already makes arrays of detector elements for monitoring light power. And Gemfire has an innovative approach to making arrays of variable optical attentuators (VOAs) (see Gemfire Comes Out Blazing). VOAs are used to adjust the light power in adjacent channels in DWDM systems, to reduce the likelihood of interference.
Right now, Wavesplitter and Infineon have made a joint product by glomming together a WaveSplitter AWG and an Infineon detector array, using a process called "flip chip bonding." Similarly, Wavesplitter and Gemfire's product is an AWG and VOA array linked together using fibers. The company hopes to shift to a bonded interface sooner or later.
Prototypes of these modules, which can support as many as 40 DWDM channels, are on show at WaveSplitter's booth at the ECOC exhibition. The AWG with power monitoring is being prepared for Telcordia reliability testing. WaveSplitter expects to ship engineering samples this quarter and go into commercial production in the first quarter of 2002.
"The next product advance would be to put all three [devices] together in a single module," says Bill Diamond, WaveSplitter's president and CEO.
The big issue that's driving AWG developers like WaveSplitter to come up with these products is the concept of dynamically reconfigurable networks. This is "point and click" service provisioning -- enabling service providers to set up and tear down light paths across optical backbones from a remote console without having to send engineers out into the field to manually reconfigure or adjust equipment.
Although this sounds great in theory, it's tough to do in practice because every path has different optical characteristics. As a result, the power needs to be adjusted on every link to optimize performance and prevent problems in adjacent paths. To make matters even more complicated, this has to be done for the primary and the backup route on protected connections. Otherwise, switching over to the backup route when the primary goes down would propogate problems throughout the network.
"As soon as you begin to route traffic dynamically, you have a situation where you need to balance channel power on a continuous basis," says Diamond. In other words, power monitoring and adjustment needs to be built into DWDM networks at every node.
As noted, most AWG manufacturers are developing products that address this requirement but are doing it in different ways. And right now, WaveSplitter's approach appears to be paying off.
First off, let's take a closer look at its joint product with Infineon. At least two other startups -- Bookham Technology PLC (Nasdaq: BKHM; London: BHM) and Kymata Ltd. (now part of Alcatel Optronics [Nasdaq: ALAO; Paris: CGO.PA]) -- also have products that integrate AWGs and power monitors.
However, Bookham and Kymata have made different sorts of devices. Both of them have made separate power monitoring devices using their AWGs. But they haven’t made a mux/demux widget with built-in monitoring, which is what WaveSplitter has done.
Built-in monitoring reduces costs considerably, according to WaveSplitter. It also means that power monitoring just becomes part of the network; it’s not something that has to be added as an afterthought, possibly at much greater expense.
The downside of WaveSplitter’s approach might be that the bonding process between its AWG and Infineon’s detector array is a possible source of reliability problems -- particularly as its AWG has to be kept at a constant temperature to work properly. Bookham and Kymata don't have this issue, because their power monitoring has been integrated into the same piece of semiconductor material as the AWG.
WaveSplitter's monitoring might also fall short of what some service providers will require. Many of them are likely to ask for optical signal-to-noise ratio monitoring as well as power monitoring, according to experts, and WaveSplitter can, so far, only do the latter.
Now let’s look at WaveSplitter’s other joint development project, with Gemfire: to make a VOA multiplexer.
Here again, a bunch of AWG manufacturers -- including NTT Electronics Corp. (NEL), JDS Uniphase Inc. (Nasdaq: JDSU; Toronto: JDU), Lightwave Microsystems Corp., and Bookham -- already have such modules. What happens inside the modules, however, differs from one company to the next. JDS, for example, simply links together a separate AWG and VOA with fiber, while Bookham integrates both devices in a single piece of silicon.
As already noted, WaveSplitter uses fiber to link its AWG with Gemfire's VOA but is hoping to move to a bonded interface sooner or later. This isn't taking integration as far as Bookham but enables WaveSplitter to use the most appropriate materials for each device: silica-on-silicon for its own AWGs and polymer for Gemfire’s VOA arrays, according to Diamond. “We don’t need to be hung up on the fact that different materials are required,” he says.
The upshot, according to WaveSplitter, is much better performance than competing products. It cites an attenuation range of 25 decibels for its joint development with Gemfire, adding that existing products from other vendors typically have a much smaller, 10 dB range. WaveSplitter also cites low power consumption (6 watts) and low polarization dependent loss (0.5 dB).
— Peter Heywood, Founding Editor, Light Reading