Optical gear finds home in courts

Use of free-space optics in the New York court system started as a response to an emergency need, but now the technology has proven to be reliable enough to be a trusted secondary connection for many court facilities.

Use of free-space optics in the New York court system started as a response to an emergency need, but now the technology has proven to be reliable enough to be a trusted secondary connection for many court facilities.

The laser transmission technology was pressed into duty on Sept. 17, 2001, to restore WAN connections to three Manhattan courthouses left isolated by the Sept. 11 World Trade Center attacks.

The free-space optical gear beams data through the open air on a laser, eliminating the need for optical cabling to carry the signal. The technology requires a clear line of sight between the sending and receiving devices, and fog and heavy snow can shorten the maximum transmission distance of 6,562 feet.

After the attacks, two of the isolated courthouses in downtown Manhattan were within sight of a third that was still connected to the state network, so Sheng Guo, the CTO for the New York State Unified Court System, installed pairs of free-space optical units from Canobeam between them. The court’s LAN switches plugged into Ethernet ports on the Canobeam boxes, which converted the traffic to an optical signal.

The third cut-off courthouse was located across the street from a carrier hotel facility that was still in operation, so Guo installed a pair of the Canobeam devices to give the courthouse access to public networks. Through the hotel, the courthouse was plugged into the state court network at another downtown courthouse.

This third courthouse also had 640 IP phones installed as part of a trial of Nortel voice-over-IP gear, and this voice traffic also was beamed through the carrier hotel to the court network. To handle voice, the Canobeam units require that the traffic be fed to it via an Ethernet interface. The traffic from those IP phones was fed into data switches, transported over the Canobeam link, split out from the data stream at the other end and dropped onto the public phone network via primary rate interface ISDN, Guo says.

Saved again

The free-space optical gear did so well that Guo called on Canobeam again when the state was in danger of losing its OC-3 fiber connections to four upstate courthouses because the optical service provider, Telergy, had filed for bankruptcy. While Telergy never actually shut off services, Guo had to assume it might do so at any time and had to devise a fallback plan for the Buffalo, Rochester, Syracuse and Binghamton courthouses it served.

So he bought more Canobeam equipment and installed it on the buildings in Buffalo, Rochester and Syracuse and pointed them at other government buildings that were tied into the New York State government fiber network. There was no way to connect the Binghamton court building to the network, and so it remained in danger of being cut off.

As it turned out, bankruptcy judges prevented Telergy from cutting off service until a new OC-3 carrier, Time-Warner, was chosen and connected to the buildings. But the Canobeam gear was there just in case. “When you’re in a bankruptcy procedure, you never know what’s going to happen,” Guo says.

The laser devices cost about $36,000 per installed pair, and that relatively low price makes them a candidate for an ongoing project to link three-site court campuses in Queens and the Bronx.

In each case, the sites are connected via two fiber lines: from Point A to Point B, and from Point B to Point C. Guo used Canobeam gear to connect Point C back to Point A to form a loop. The primary route uses only the fiber connections, with the free-space laser link a backup if the fiber fails, he says. “Canobeam is not the preferred connection. If it snows, performance is degraded, but we’ve had no complaints,” he says.

In the Queens campus, using the Canobeam gear cost about $150,000 less than it would have cost to use fiber, Guo says, and was much faster to install. Getting permits to run fiber under city streets would have taken months.

Even so, Guo has replaced an 11M bit/sec 802.11b wireless connection between courthouses in Riverhead, N.Y., with a Gigabit Canobeam DT-55 link. The backup is a T-1 from each building to a hub site in Manhattan 90 miles away.

Lasers proliferate

And Guo says he plans to install another pair as the primary connection between a new judicial research institute being built in White Plains, N.Y., to an existing courthouse on CourtNet. The gear also is a candidate to connect buildings within five other court campuses in the New York City area.

Guo tried installing some of the Canobeam devices indoors and pointing them through the window, but discovered tinted glass can impede performance. He also found out the inside devices are at risk of being bumped off their aim by careless humans. “A cleaning lady mopping the floor moved the Canobeam, and everyone was screaming,” because the laser wasn’t hitting the receiver, Guo says.

Despite these shortcomings, Guo deems the gear suitable as the primary data link in some cases as long as it has an emergency backup. “We are moving use of it from crisis mode to operational mode,” Guo says.