The aftermath of 9/11. What light through yonder window breaks? [free-space laser link]

The local communication infrastructure was hit hard by the events of September 11. Financial corporations with an urgent need to transmit high-speed data between offices in physically separate locations were particularly affected, and scrambled to come up with viable alternatives to disrupted fiber-optic cables and RF-based wireless networks. According to a report in Conformity (December, 2001), Merrill Lynch turned to free-space optics for setting up a communication link between its office in lower Manhattan and backup offices across the river in Jersey City, New Jersey. The data were transmitted across the 1.6-mile distance via a laser beam. While free-space optics has been around for over thirty years, and has been investigated for many exotic applications such as satellite-to-satellite communication, it has not been used widely in mainstream applications. Merrill Lynch opted for a free-space laser link because such a system could be up and running within a few hours, following a disaster such as the WTC collapse.