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.

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.

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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.