WDM moves to metro networks

Optical technologies such as wavelength division multiplexing (WDM) are moving swiftly from traditional long-haul segments into the metropolitan and access networks, and picking up IP (Internet protocol) momentum along the way.

As the cost of WDM goes down and the capacity demand in city networks goes up, there is a trend for service providers to deploy the technology closer to the customer, said Idris Vasi, director of optical networking, Asia-Pacific, Cisco Systems Inc.

With WDM, different colours of light are multiplexed and transmitted as separate channels within a single fiber. Current state-of-the-art WDM enables 64 to 80 channels of light to be transmitted per fiber.

According to market research and consulting firm RHK, 98 per cent of WDM spending in 2000 went to the long-haul segment, with the rest in the metropolitan networks.

By 2004, Vasi said the share of WDM spending in metropolitan networks is expected to go up to 21 per cent. Overall, the five-year metro opportunity will amount to US$2.7 billion.

Most service providers, however, are still using fiber to deploy raw capacity. But to generate revenue, they will need to start deploying services such as hosting and virtual private networks, said Vasi.

“With the deregulation of the telecommunications market, service differentiation becomes very important. SingTel and other companies now have to worry about service velocity,” he added.

This is where optical IP comes into the picture. “Optical IP takes the intelligence of IP and the capacity of optics, and merges them together,” said Vasi.

Deployed in the metro segment, optical IP helps to remove the bottleneck between service providers and corporate LANs (local area networks).

There are a lot of IP-driven applications at the service provider’s point of presence (POP), with caching facilities and the generation of local content, said Vasi.

A lot of services at the POP are then sent back to the metro networks. However, there are performance constraints due to existing bandwidth limitations at the access and metro level.

“Existing networks already deployed based on time division multiplexing cannot meet the demand of packet-based traffic,” said Vasi.

“Service providers deploying optical networks today have to be aware that the growth is coming from IP, and that they will have to integrate IP into optical networks.”

Cisco’s optical IP strategy provides one avenue for such integration. “We take IP platforms and enable them with optical interfaces, WDM interfaces, and we add packet technology to optical platforms,” said Vasi. The company’s IP-based optical control plane also incorporates multiple protocol layer switching with IP intelligence.

To tackle the fourth component of the optical IP strategy, network management, Cisco will be working with partners to provide the different software pieces required.