Managing Optical Networks

Managing Optical Networks

Optical networks have a number of unique management requirements that necessitate new techniques. There are currently no standards for carrying management information in optical networks, so carriers may be forced to retain electrical interfaces so that they can pinpoint faults. There is also currently no way to support error-correcting protocols on optical networks. Carriers still also need electrical interfaces to regenerate the right color light; because there is currently no standard for connecting one shade of blue light to another shade of blue light, for example, carriers must rely on a complete package of transmission equipment and switching from the same vendor.

Adding more wavelengths presents service providers with a new challenge: cost-effectively managing the increasing number of wavelengths to provide fast, reliable services to end customers. Digital wrappers promise to provide network management functions such as optical-layer performance monitoring, error correction, and ring-protection capabilities, on a per-wavelength basis. These digital wrappers are standardized as part of submarine cabling systems, and both the ITU and the OIF have accepted the standard for landline fiber systems. Lucent has also unveiled its proprietary version of the standard, called WaveWrapper, which was developed by Bell Labs. The WaveWrapper works like this:

1.       It places a small digital wrapper around each input wavelength. The wrapper carries information, such as restoration signals, what type of traffic is in the wavelength, and where the traffic is headed.

2.       As the wavelength moves around the network, the nodes read the header. They scan for originating and terminating details, information about whether it's an IP or ATM signal (or another protocol's signal), and commands such as strong forward error correction.

3.       Systems determine the health of the signal, whether it needs to be rerouted, and whether the necessary equipment exists to receive the signal at its intended destination.

Lucent has submitted WaveWrapper as a standard to the ANSI Telecommunications Standards Committee, the OIF, and the ITU.

Remember that with intelligent optical networking, the challenge is to deal with each wavelength individually. It is necessary to understand what is happening on each wavelength in order to route and rearrange a wavelength across different carriers' networks. To understand the wavelength's personality, the wavelength must be monitored, and this capability takes intelligence. Optical network operators will therefore require new tools, including optical channel analyzers, power-balancing techniques, tunable filters, physical restoration techniques, and control plane signaling. An optical probe will be another very important element in the optical equation because it will provide the capability to look into a wavelength to determine its behavior, thereby assuring intelligent end-to-end optical networking, with real-time provisioning capabilities and wavelength management opportunities (see Figure 12.10).

Figure 12.10. Optical probe monitoring

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