Laser-Excited Fiber Provides Highly Visible Escape Routes

Dr. James P. Smith

An emergency onboard an offshore oil installation is too often fatal. Hundreds of yards of passageways can become a deadly maze when smoke and darkness obscure landmarks and escape routes.

Lifor Ltd., which specializes in laser applications, has found a fertile market niche by satisfying the need for reliable, inexpensive emergency escape-route illumination.

The Scottish company has developed TrailLight -- a laser-excited fiber optic cable that emits a green light and is visible in dense smoke. Because the fiber display is not electrically powered, it will not cause fire or explosion and can be used in corrosive environments as well as underwater. David Stevenson, managing director of Lifor, said oil rigs represent a large, untapped market for the technology.

David Stevenson, managing director of Lifor Ltd., demonstrates his company's laser-excited fiber optic cable, which he describes as a low-cost solution for illuminating emergency escape routes. The advantage of green light is that it can be easily seen even through smoke.

Stevenson said the unit's dimensions are determined by the size of the batteries, which are conservatively specified for three hours of operation. The batteries and laser are contained in a box measuring 13 × 13 × 20 cm. The fibers are approximately 6 mm in diameter and up to 100 m long. "We have a patented system that is basically three cables that are bundled, and the light is multiplexed between them to create the impression that a pulse of light is traveling in one direction to indicate which way to walk," he said.

The advantage of having a bright green light is that this wavelength is at the peak of the human eye's response and highly visible -- even through smoke. Stevenson listed several possible applications: escape routes for public buildings and tunnels, architectural lighting, and marking night landing fields and helicopter pads. "Since the fibers are impervious to water," he said, "underwater operation is possible, and we have had some very successful water trials."

Lifor works closely with the University of St. Andrews in St. Andrews, UK, where much of the laser technology is developed. They hope TrailLight will be commercially available by May, with first installations the following month. Both the company and the university are members of the Scottish Optoelectronics Association, which was established in 1994 to support the growing optoelectronics community in Scotland.