Until recently there was no way to perform network monitoring on the optical networks. Engineers could only spot problems by counting bits after traffic went through an optical to electrical conversion. Craig Armiento, director of optical network engineering at LightChip, Salem N.H., says that technologies to monitor and manage optical networks are not that far off in the future.
How popular is dense wavelength division multiplexing (DWDM) optical technology?
Armiento: DWDM is quite extensively used in long haul networks across the country, across the ocean. Many of these employ up to 80 wavelengths at a time. So DWDM is very well ensconced in the long haul networks.
Where is DWDM technology heading?
Armiento: What we are seeing more recently is DWDM beginning to be deployed in what's called the metro area: Networks that are confined to a metro region, typically in rings that go around cities that have spokes to them. We're seeing wavelengths being used in these metro ring areas for the telecom carriers, and the enterprise service companies. We're also seeing a growing use of DWDM in cable TV networks. The big cable companies are beginning to deliver services that are bigger than the old video delivery services with the growth of cable modems and cable telephony. As a result of this the networks that were in place had to be upgraded to carry two-way communications. In the old broadcast days it was unidirectional broadcast video services, now with telephony and data it's more of a two-way communication. The emergence of these interactive services is driving the cable industry to start using DWDM in an aggressive fashion.
What methods are there for judging the performance on optical networks?
Armiento: The old way, the familiar way for checking on the quality of service was bit error rate. Networks are migrating to a mode of operation where not all wavelengths are converted to electrical at each node. There is a trend in the networking world to control bandwidth on the optical layer. That is switching wavelengths as opposed to doing optical to electrical conversion at each node. What happens then is that you no longer have access to the bits. You need another way of monitoring the health of signals while they are still in their optical form. That's what we do, we provide another layer of performance monitoring, this time at the optical layer, which is supplementary to the conventional approaches that network operators have used in the past.
Why is it important to monitor a network on the optical layer?
Armiento: The network is getting more complicated, more and more wavelengths are added each wavelength now carries 10 gigabits of data. You have to make sure that you monitor these wavelengths because there's a huge amount of money riding on each wavelength. You can imagine the lost revenues associated with loosing a wavelength if your providing 10 gigabits of service. As wavelengths become more prevalent in the network and become one of the units of measure of bandwidth that you will need the ability to monitor the optical layer.
What is the current method of troubleshooting an optical network fault?
Armiento: Now if you think there's an optical problem somewhere, you send a guy in a truck and he takes a portable spectrum analyzer and plugs it into the network where he thinks the problem is. Network operators now don't have visibility into what's going on with their DWDM signals, unless they have an optical to electrical conversion at every node.
|"Network operators now don't have visibility into what's going on with their DWDM signals, unless they have an optical to electrical conversion at every node." -- Craig Armiento, director of optical network engineering at LightChip, Salem N.H.|
What is LightChip's reaction to this situation?
Armiento: What we're trying to do is replace much of the traditional truck-roll model with something that allows the operator to have visibility to all the wavelengths in the fiber at key points through out the network.
How is optical monitoring currently used?
Armiento: Optical monitoring's primary use right now is to diagnose problems. The corrective actions often times given the way companies work now is to roll the truck. You save the guy the legwork because a lot of time is spent poking around various places in the network trying to diagnose what's going on. With LightChip's solution you can target the problem precisely.
What are some future trends in terms of optical network monitoring and troubleshooting?
Armiento: There is a trend going on that will allow you to remotely control elements from your network operations center. There are things that happen to lasers for instance where the optical power degrades, it could be a sudden thing or it may be gradual degradation. What happens is by the time you've seen it, if you are just looking at bit errors, then it's too late, possibly impacting your service level agreement causing you lost revenues and costing you fines. LightChip's approach to this is to monitor things at the optical layer, and to be able to detect these gradual degradations so that you can take corrective actions before the customer ever knows there's a problem. So preemptive monitoring is going to be key to managing service level agreements and to ensure a steady flow of revenue from hi-bandwidth services.
How far off in the future is remote optical network management?
Armiento: I think that we're probably two or three years away at most. It's going to have to be the mode of operations for many networks. This is not blue sky this is real and there is a lot of activity going on.
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