By John McHale
NASHUA, N.H. — Engineers at Sanders, a Lockheed Martin Company in Nashua, N.H., are using fiber optic technology combined with an all-band laser source for infrared countermeasures (IRCM) applications to reduce weight, complexity, and cost.
The power available from the all-band laser, together with the flexibility and low cost of fiber optic cables, promises to bolster countermeasures against infrared, or "heat-seeking," missiles, Sanders officials say. Infrared missiles typically home in on the hot exhaust of jet aircraft engines.
A recent demonstration of the technology "showed that fiber optic technology provides a highly effective means of directing laser energy in an [infrared] countermeasures system," says Tom Evans, the Sanders manager of the Multispectral Countermeasures (MSCM) program. The system uses the laser to create a separate "hot spot" to lure the infrared missile away from its primary target.
Currently, similar laser jammers use optical coupling to direct the energy.
Previous methods use a series of mirrors in an enclosed tube, where the mirrors control the laser beam as it moves through the tube, Evans explains.
Tests last month at the Sanders Merrimack, N.H., test range featured a modified U.S. Army Advanced Threat Infrared Countermeasures (ATIRCM) directable jam head to support a fiber optic path from the laser through the jam head output aperture. The Sanders-designed laser system generated more than four watts of jamming energy into a mid-infrared fiber optic cable.
A fiber optic rotating joint from Litton Poly-Scientific in Blacksburg, Va., enables the jam head to turn 360 degrees toward a target, Evans says.
The fiber optic device is in the shape of a robotic arm with several elbows, each of which that has a beamsteering galvonometer or mirror. These devices steer the beam to the next elbow point. Designers use these devices because the optics make it difficult to keep the beam aligned, Evans says.
The fiber optic cable, developed by the U.S. Naval Research Laboratory in Washington, performed perfectly without damage and with only negligible optical loss, Sanders officials claim. The effort also verified the precise pointing accuracy of the ATIRCM system using the fiber optic technology, they say.
Still, there are potential drawbacks. Fiber optics produce a beam that diverges faster than a normal laser and the device needs a collecting mirror to keep the beam together, Evans explains. The biggest advantage to using fiber optics is low cost and weight, Evans says.
Future demonstrations under the MSCM ATD will include the use of a multi-band semiconductor laser as an IRCM source. Experts at the Massachusetts Institute of Technology/Lincoln Labs in Lexington, Mass., are providing semiconductor laser materials for the fabrication of the semiconductor laser.
The semiconductor laser, developed by Decade Optical Systems of Albuquerque, N.M., will be connected by fiber optic cables to the Agile Eye directable jam head that was designed by Sanders for the U.S. Navy`s Tactical Aircraft Directional Infrared Countermeasures (TADIRCM) program.
The demonstration was under the aegis of the U.S. Army`s MSCM Advanced Technology Demonstration program. Sanders received a contract from the Army`s Communications-Electronics Command in December 1996 to develop and demonstrate countermeasures against infrared missiles as well as pre-planned product improvements for IRCM technology for ATIRCM hardware and other assets. The Army programming office for ATIRCM is at Redstone Arsenal in Huntsville, Ala.
Sanders engineers lowered costs and improved performance by using fiber optic cables with the U.S. Army Advanced Threat Infrared Countermeasures all-band laser.
