Let There Be Light

By W. Eric Martin
Sometimes there's still life in communication methods once thought dead.

That's the lesson Sheng Guo, chief technology officer for the New York State Unified Court System, learned after the Sept. 11 attack on the World Trade Center destroyed a Verizon switching office, cutting off telephone and e-mail service for 2,500 users at three courthouses in the area.

"We desperately needed something to bring them back online," Guo said.

Over the next three days, Guo and other court employees debated how to get reconnected. The solution came when Guo recalled seeing an ad for Canobeam, Canon's version of a wireless network technology called free-space optics (FSO).

Everything Old Is New Again
Just as Morse code can be sent by opening and closing the windows of a lantern, Alexander Graham Bell used modulated sunlight in the 1880s to create a "photo-phone," a device soon replaced by Bell's better known communications system. After lasers were developed in the 1960s, NASA unsuccessfully tried to use them to communicate with its Gemini 7 orbiter.

The United States Navy and Air Force also experimented with laser communication, but FSO -- as the technology is known today -- only really started to grow when the need for huge bandwidth was seen in the private sector. Today, transmission speeds of up to 1,000 Mbps are possible on FSO systems, purely by use of lasers through open air.

The sending and receiving devices must have a clear line of sight between them -- as was the case with two cut off courthouses, those at 60 Centre St. and 123 Williams St., which were within sight of a third courthouse at 31 Chambers St. that was still connected to CourtNet, the courthouse network. By using the Canobeam equipment, Guo and his team connected the first two courthouses to the 31 Chambers St. courthouse, so they could access CourtNet.

A third courthouse was isolated from the network at 71 Thomas St. A Canobeam was used to connect that courthouse to a hotel across the street, which still had Internet access. The courthouse could then piggyback on the hotel's Internet access to ultimately hook up to CourtNet through another downtown courthouse at 25 Beaver St.

After calling Canon the night of Friday, Sept. 14, Guo was convinced the technology would satisfy their immediate needs and tried to work out a deal. "They said they needed a PO [purchase order], but I sent them a signature and told them to trust me," he said. "In this emergency, I said, 'You need to sell us that equipment now, and the PO will follow.'"

To Guo's surprise, Canon made the deal and trained three of his staff members that Sunday on how to install and use the equipment. Data service was restored by the night of Sept 17, said Guo.

"In a typical installation, approval from the building management is required for mounting equipment," he said. "In addition, the contractor was supposed to conduct a site survey and submit a price quote for the fiber wiring from the Canobeam location to the core switch of the courthouse. Because this was an emergency, we went ahead with the installation anyway. The contractor was creative in running temporary fiber cables to bring IP connectivity back on the same day."

FSO is ideal for a quick link during disaster recovery, according to Ken Ito, assistant director for Canon's Broadcast & Communications Division. Unlike radio or microwaves, FSO provides a lot of bandwidth and doesn't require FCC approval.

FSO to the Rescue -- Again
In early 2002, Guo turned to Canobeam once again when Telergy -- the telecom provider that serves courthouses in Buffalo, Rochester and Syracuse -- filed for bankruptcy.

"If they shut down service, we didn't have a backup plan," Guo said. "We could ask someone else to provide service, but normally that would take a lot of time."

Instead of relying on others, the do-it-yourself Guo purchased more Canobeam equipment and connected the courthouses in those three cities to other government buildings in the New York state government network. In the end, the bankruptcy judge prevented Telergy from shutting off service, but the FSO system provided the insurance Guo needed.

Guo has since installed Canobeam in courthouses in Queens and the Bronx to back up existing communications. "In each case, we have three buildings with fiber from building A to building B, and from building B to building C. Ideally we want a ring, a connection from building C to building A to complete the loop," he said. "If it's possible to have fiber, we do that, but in Queens the cost would have been in the $150,000 range. The Canobeam cost $30,000, plus another $10,000 for installation -- a quarter of the cost." Choosing FSO over fiber also bypassed the months of waiting time normally needed for approval to run fiber underground.

Two courthouses in Suffolk County on Long Island have also been connected by Canobeam FSO systems. "In the past, we had a slow connection from the T1, and people used to complain about performance," Guo said. "That's a nonissue now. Everything's working."

Future Orders in the Court
Guo plans to use Canobeam to connect facilities in White Plains and Albany, and court campuses in New York City, but FSO will continue to be used either as backup to a fiber connection or in concert with another medium. "It's possible to have misalignment," he said. Also, when it snows heavily, as it often does in Buffalo and Rochester, the performance of FSO will be degraded as the snow interrupts the laser beam.

"If a bird flies in front of the laser, for example, the network goes down for a fraction of a second. The user doesn't know it, but our system does," Guo said. "It's a potential concern, but I haven't yet run into a situation where it doesn't work."

"We try not to say the technology replaces radios, but complements them," Ito said. "FSO doesn't like fog, but radios do. Radios don't do well in rain, but FSO is okay. There's a good balance between the two."

Ito said that building movement is another concern for those interested in using FSO. Heat during the day might cause one side of a building to expand, creating misalignment of the beam and loss of connectivity. To account for this movement -- as well as earth tremors and other alignment issues -- FSO systems must either spread out the beam, which reduces its effective distance, or include autotracking mechanisms, so they can adjust to moving buildings. Canobeam's DT-50, for example, works best to a distance of about 2 km.

"In the future, we will continue to look at this as a good alternative," Guo said, not only for the e-mail sent and received by the court's 15,000 employees and the access to civil and criminal case histories, but also for voice communication over IP phones and videoconferencing.

"We're in a tight budget and are always looking for ways to save money," Guo said. "Many government facilities are clustered in a downtown area and still paying a carrier a few thousand dollars to connect with the building next door. In that case, I'd strongly recommend people look at their network infrastructures. Otherwise you're just paying too much money every single month."

W. Eric Martin is a freelance writer in southeastern Massachusetts.