High-tech battlefield: light source offers alternative to radio.

Imagine the entire Navy operating in complete radio silence.

The concept sounds like a science fiction scenario, but it is not entirely far fetched, considering recent developments in technology that employs light as a new medium for military communications.

Light frequencies--in this case, the microscopic waves of infrared light that lie between the visible and microwave portions of the electromagnetic spectrum--are not a new discovery, by any means. For years, near infrared light waves have been exploited in mainstream gadgets--most notably as the medium that enables us to operate TV, DVD and CD players by remote control.

Under a Navy contract and with corporate funds, a San Diego-based company, Torrey Pines Logic Inc., has developed a tiny transmitter and receiver system utilizing prisms that, when engineered into an attachment that fits eyepieces of optical devices--such as binoculars or gun scopes--allows users to beam infrared light pulses and, in the process, exchange voice or digital data.

The technology is viewed as a significant development, because it could help diminish the military's reliance on communications over radio frequencies.

At first, it sounds like a rather simple process. Two users with customized binoculars look at each other and communicate. The optics in one eyepiece transmits light signals and the other eyepiece receives light signals.

But making the technology useful to the military is far more complex, says David Copenhaver, of 4ISR LLC. The company markets the technology, which is known as LightSpeed.

Data transmissions via infrared light have not been done before, he asserts.

"This is old, old technology that has a fantastic capability that has been overlooked for years," says Copenhaver. Infrared light technology is pervasive in the consumer world, but has not been exploited as a transmission medium for data.

"It is very difficult, mechanically, to do what we are doing," he says. "Optically, it's difficult. We are literally slicing off light frequencies ... and turning them into electrical impulses of data."

The Navy could choose to apply the technology in any number of ways. Attached to the back of binoculars, the technology would allow an operator along the coastline to communicate with a ship several miles offshore. That same attachment could be installed on much larger ship-mounted binoculars to allow ships at sea to exchange data.

"We miniaturized electronics into a tiny, silver-dollar size piece," says Copenhaver. "It doesn't change the use of the binocular in any way."

By plugging an ear bud into the attachment on the binocular, much like one would plug a hands-free set into a cell phone, the user could verbally communicate with another person who is using the technology. Similarly, if a laptop were connected to the binoculars, the users could share data, such as maps and charts.

The need for a non-radio frequency communications technology has become evident during military operations in Iraq, he says. "In the Green Zone, you can't just pick up your radio and talk on it." Because the frequencies are often jammed, communications via radio requires booking a time and frequency in advance, he says. Not only are those communications susceptible to interception, but radio limitations, such as the signal-to-noise ratio and distance, also are impediments.

To exchange data via infrared light, users as far apart as 12 miles can peer at each other using the optical devices, or they could direct their eyepieces towards any object that reflects light, such as a window or the bumper of a car, he says.

At the heart of LightSpeed is breakthrough technology involving infrared light-emitting diodes, or LEDs, and computer chips called applications specific integrated circuits, or ASIC, says Michael Konrad, of 4ISR.

A potentially major selling point is the vast availability of spectrum. An unlimited number of frequencies are available to transmit data in the light spectrum--from the nanometer to the micron range, he says. Unlike radio frequencies, the light frequencies are non-regulated. Because light frequencies cannot be detected, communications are virtually impossible to intercept, says Copenhaver.

"When radio was first being used, it took a significant amount of time--years--for them to come up with technology that could intercept a random radio wave. Even if someday someone comes up with a way to intercept the light communication, we are probably a few years away from that," says Konrad.

LightSpeed also would diminish the military's heavy dependence on batteries. It runs on little energy--on a quarter of a milliwatt of electricity. A single bulb on a strand of Christmas tree lights consumes 500 milliwatts of electricity.

"We can transmit very long distances with very little power, which is an important thing to military and other organizations," says Copenhaver. Radios operate at megawatts of power, he says.

To transmit at further distances using LightSpeed requires cranking up the power to only a couple of milliwatts.

The integration of the infrared light-based technology with fiber optics adds omni-directional transmission capabilities, says Konrad.

An obvious application would be military surveillance drones. "With this technology, instead of taking a camera and putting it in an unmanned aerial vehicle, and transmitting over a radio frequency, anybody on the ground, with a set of retrofitted binoculars, can look at that UAV and literally see what the UAV sees on its camera," says Konrad.

The company recently delivered 20 LightSpeed devices to the Navy, which the service will test aboard ships in exercises scheduled for this summer.

Torrey Pines currently is working on a new feature that would make LightSpeed potentially more useful in urban areas. Light transmissions can overcome the lack of direct lines of sight in urban areas by reflecting the light off shiny objects or windows, but this crude technique would not be practical in military operations.

To overcome this limitation, the company is developing a communications-relay device. About the size of a half-grapefruit, it could be installed on the side of buildings.