DENVER -- Cable Next-Gen Technologies & Strategies -- Faced with the same challenges as their telecom rivals, cable operators are looking for advanced ways to add bandwidth to their optical transport systems in a cost-effective way, and to protect that bandwidth in a way that doesn't eat up resources unnecessarily, two Infinera executives said here today.
At a packed-house breakfast panel sponsored by Infinera, Gaylord Hart, director of the vendor's MSO market segment business, and Yalin Wang, senior director of product planning, laid out at least one future option: a network built on photonic integrated circuit (PIC) technology and shared mesh protection of the optical transport network. That setup, Infinera says, can help cable operators add and protect bandwidth more cost effectively.
The cost of adding bandwidth is a critical issue for network operators, Hart said. At least traditionally, the revenue from selling bandwidth doesn't increase at the same pace as demand and consumption of that bandwidth. This fact makes it essential to protect margins by introducing greater efficiencies.
The common approach of adding 100G transponders to the network doesn't scale to meet today's demands, he said. Using PICS, it is possible to create a single 500 Gbit/s superchannel using fewer components. "We can come up with a relatively compact line module that supports a 1 Tbit/s, 10-carrier superchannel line card based on PIC," Hart said. The non-PIC option for scaling capacity to 1 Tbit/s levels, such as a 1 Tbit/s transponder; that is about eight years off.
The next generation of superchannels will be implemented in a new way, he said. Instead of using the ITU-approved approach, which creates a guard band between each of 10x100 Gbit/s wavelengths (essentially wasting about 50% of the fiber capacity), the next generation will use FlexGrid channels, which places 10 carriers closer together, treating them as a single entity and deploying only two guard bands, one on each end of the 1 Tbit/s signal.
When it comes to protecting the optical networks, Wang said, fiber cuts remain the single biggest problem. Construction is causing the majority of those cuts – even though not-so-friendly squirrels do their share of damage. In the US, there are still 100 fiber cuts daily, but in developing countries, there is one fiber cut every minute.
In traditional fiber networks, such as those built using Sonet-based technology, the fiber is protected by a one-to-one ratio of working to backup fiber, and the restoration threshold is traditionally 50 milliseconds. That's a hard time to match with coherent technology, which lets optics travel farther without regeneration but also creates slower recovery times, Wang said.
"A new ITU standard is emerging, G.808.3 or G.SMP, that creates a shared protection path to be used by two working paths that don't share the same risk," he said. "In the case of a failure, the network sends a message to wake up the pre-planned protection path."
According to Infinera, this standard uses OTN switching for shared protection at the transport layer to achieve the 50 ms switchover at a lower cost in coherent optical environments.
He also made a strong argument for the cable industry to examine the potential of doing recovery at the optical transport network layer, not at the IP/MPLS layer. The IP/MPLS layer can detect network failures and route around issues, but that approach results in a lot of traffic bouncing from router to router and using up costly router ports. OTN restoration can be the first line of defense in a more cost-effective approach to the critical issue of restoration.
— Carol Wilson, Editor-at-Large, Light Reading