US research and development of infrared laser communication system: can not eavesdrop high security

According to a report on November 1, Beijing time, according to the American Discovery Channel report, how to transmit information without being eavesdropped has always been a challenge facing the military. Infrared laser communication can solve this problem. Currently, the Air Force Research Laboratory at Wright-Patterson Air Force Base, Ohio, is working with Space Photonics in Fayetteville, Arkansas to develop an infrared laser called "free space optical communication." system. This kind of laser communication carries more information than other wireless signals such as Wi-Fi and is more secure.

The reason why infrared laser communication has high security is due to the characteristics of this laser. The infrared laser beam is so narrow that the enemy cannot eavesdrop unless they are on the transmission line. This is in stark contrast to radio waves, which generate "lobes" near transmission points, making it possible for hackers to eavesdrop. If a person manages to enter the transmission line of the laser beam, and then attempts to "wire tap", the laser beam will be interrupted. This interruption will immediately alert the sender that someone may be trying to eavesdrop on the line. Because the laser system works in a "line-of-sight" way, the sender can determine whether someone is trying to intercept the information and then re-launch it.

Terry Tideville, chief engineer of Space Photonics, said: "Its security is innate." Recently, the company signed an agreement to commercialize the technology they developed and then sold it to the defense. unit. In addition to high security, laser communication can also cram large amounts of information into a very narrow beam. Wi-Fi can transmit several megabits of information per second. In contrast, the amount of data carried by an infrared laser beam can reach thousands of times that of Wi-Fi.

In addition to space photonics companies, other companies are also developing laser communication systems for the military, including ITT Exelis. Gary Tarantino, head of the advanced systems and innovation department at ITT Exelis, said they won a $ 7 million contract to develop a ship-to-shore communication system for the Navy. He said: "We are designing this kind of laser communication system, hoping to achieve optimization in terms of automatic operation and correction of natural electricity interference." As of the end of 2013, ITT Exelis' laser communication system is expected to surface. , The communication distance can reach about 12 miles (about 19 kilometers).

The concept of space-based laser communication was first proposed in the 1970s, and this technology is very costly. Optical fiber cables began to be widely used around the same period. The cost of such cables is lower than ordinary cables and the transmission distance is farther. The transmission distance of a space-based laser beam is usually a few kilometers. If it is between aircraft flying at high altitude, the distance can reach 120 miles (about 193 kilometers). With the continuous development of lower-cost semiconductor laser technology, costs began to fall. At the same time, the rise of electronic devices such as smartphones, laptops and tablets has increased the demand for greater data capacity.

In the civilian market, many companies use optical cables to increase the capacity of cell phone signal towers to allow cable networks to carry more data. On the battlefield, laying fiber optic cables is obviously not a realistic approach. Like civilians, the US military found that they also needed to transmit large amounts of data, so they refocused their attention on laser communications. In the mid-2000s, Afghanistan ’s Bagram Air Force Base installed a fixed, small-scale system.

Laser communication has many advantages, but there are also a series of problems, one of which is laser beam aiming. Early systems used large receivers, or let the laser beam diffuse, reaching a few feet wide when it reached the receiving point. The method now adopted is to combine the optical device of the receiver with the universal bracket. By changing the direction of the lens, the space photonics company allows the laser beam to always hit the receiver-allowing the universal bracket to rotate the receiver, basically completing the alignment work, and the optical device to complete the remaining work. The method adopted by ITT Exelis mainly depends on the universal bracket.

In 2010, AOptix verified a system using adaptive optical instruments for the Air Force. This method draws on the design of the telescope to ensure the transmission and reception quality of the laser beam. The 1.5 micron wavelength laser beam can be efficiently transmitted, but humid air and dense fog will reduce the signal transmission range. AOptix combines their system with a radio frequency transmitter as a backup system. No technology is perfect. As the performance of tracking systems and signal processing systems continues to improve, laser communication technology will continue to develop. Tarantino said: "A new generation of technology is constantly maturing."

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