CDMA moves to optical networking: CTC offering accommodates 128 OC-12 channels

Commercial Technologies Corp. is announcing a system that will apply code division multiple access to optical networks at Supercomm '98. CTC plans to make the system commercially available in early 1999.

The basic principle behind the system is simple: A single light source is directed through filters that block some portion of the light. By using different filters, CTC's system can accommodate up to 128 OC-12 (622 Mb/s) channels. The system broadcasts these channels to all receivers on the system, but because each receiver has a filter that matches one signal, it receives only that signal.

Bill Johnson, CTC's chief operating officer, described the process as "bar-coding" optical signals. When the receiver reads an appropriate bar code, it picks up that signal. This system, along with the broadcasting of all signals to all receivers, moves the all-optical network closer to reality.

"We can do add/drop, cross-connect and restoration all at the optic level," Johnson said. "We can take the electronics out of the middle."

The idea of applying CDMA to photonic networks is not new, but it had been dismissed because the phase element of the optical signal makes it difficult to eliminate interference between photons in separate optical CDMA channels, Johnson said.

CTC has solved that challenge, he said, but "that technology is very proprietary," and until a patent is issued, the company won't explain how it works.

CTC will target competitive local exchange carriers initially and long-distance and customer premises equipment markets later.

It is difficult to gauge how the market will respond to CTC's solution until it's available for deployment, said Mathew Steinberg, director of optical networking at Ryan, Hankin and Kent.

"[Optical] CDMA potentially offers very low first-installed cost since you share a single light source for many channels," Steinberg said. "The carriers are interested in both installed first cost and total cost over a given time period. It's another alternative for the carrier to add capacity."

Cambrian Systems and Lucent Technologies are collaborating to make their dense wavelength division multiplexing technologies interoperable. The companies have completed initial testing of Cambrian's OPTera Metro DWDM systems with Lucent's WaveStar point-to-point systems, including the OLS 40G metropolitan system and the OLS 400G long-haul version.

"We've tried to focus on two applications," said Kathy Szelag, global strategy vice president for Lucent's optical networking division. "One is [Cambrian's] metro system tied to our long-distance system, which would ostensibly be tied to their metro system on the other end. The other is [a connection] between our two metro systems." Cambrian's ring product would run in a business building or campus. Lucent's across-the-city switch would tie two Cambrian rings together, she said.

Today's DWDM networks are non-interoperable, which locks carriers into a single-vendor solution, said Solomon Wong, assistant vice president of marketing for Cambrian. "For DWDM products to be used, they have to work from the customer premises all the way through [the network] into the backbone. You have to interwork these various systems on the physical layer and on the management layer." Both companies are pushing WDM standards.

The Cambrian/Lucent collaboration is important for two reasons, said Mathew Steinberg, director of optical networking at Ryan, Hankin and Kent. The first is that the equipment interoperates, the second is that the two will work with a common management system.

"Carriers want interoperability because they want to have choice in their systems [and in the equipment] that they procure," Steinberg said. It's important that the equipment work together on both the physical and software levels so the equipment can be managed from a single operating system or network management platform, he added.

Cambrian's protocol-independent OPTera allows non-Sonet formatted payloads to travel across the metropolitan area network. "This gives carriers a new alternative that doesn't exist with Sonet or other WDM products," said Wong, who added that Cambrian wants to extend that capability into the wide area through collaborative efforts with other vendors.