Current status of development of long-wave infrared wireless laser communication technology

According to the transmission theory of laser in the atmosphere and a large number of field experiments, the atmospheric influence on long-wave infrared laser with a wavelength of 8-14μm is smaller than that on near-infrared laser. If the laser carrier of the wireless laser communication system adopts the long-wave infrared band, it will help reduce the influence of the atmosphere, increase the transmission distance of the system, improve the stability of the communication system, and to a certain extent break through the limitations of near-infrared wireless laser communication technology in the atmospheric channel. For a long time, the immaturity of the device has been the main reason why long-wave infrared lasers are difficult to apply to wireless laser communication systems. However, with the advancement of technology, especially the gradual maturity of a series of miniaturized and high-performance long-wave infrared key devices, long-wave infrared wireless laser communication technology is becoming increasingly practical.

Current status of development of long-wave infrared wireless laser communication technology

In fact, as early as the peak of the first wave of wireless laser communication technology research in the 1970s, the 10.6μm CO2 gas laser developed at that time became the main candidate light source for early wireless laser communication systems. Due to the limitations of the technical conditions at that time. The 10.6μm wireless laser communication system manufactured was large in size and had high power consumption. At the same time, the corresponding devices were not mature, and the signal modulation and detection technology was not ideal. In the 1990s, with the maturity of 0.8μm band and 1.55μm band devices, most wireless laser communication systems used near-infrared lasers in the 0.8-1.55μm band. Since the near-infrared short-wavelength light waves are severely affected in the atmosphere, the maximum transmission distance of the near-infrared wireless laser communication system in the atmospheric channel has always been difficult to increase, and its application is not widespread. With the further development of device technology, especially the gradual maturity of a series of miniaturized, high-performance long-wave infrared key devices, the 8-14μ long-wave infrared band with better transmission performance in the atmosphere has naturally regained attention.

In 2004, Andrew Pavelchek and others from Maxima Corporation in San Diego, USA, established a preliminary long-wave infrared wireless laser system, using a quantum cascade laser (QCL) with a power of 180mW, a wavelength adjustable range of 8-12μm, and room temperature operation as the light source, and a room temperature HgCdZnTe detector, with an average transmission rate of 155Mb/s (maximum up to 1Gb/s). In 2004, Donald Hutchinson and others from Oak Ridge National Laboratory in the United States used a waveguide CO2 laser and a Stark modulator based on an air-insulated waveguide to establish an experimental system with a transmission distance of 5km and all-weather operation. The laser output exceeded 1W, and the modulator was cooled by air, with a maximum modulation frequency of 500MHz. In 2008, Andrew Hood and others from Northwestern University in the United States analyzed and compared the current superlattice detectors and quantum cascade lasers and believed that the conditions for developing a new long-wave infrared wireless laser communication system for practical application have been basically met. They also believed that the 8-14μm long-wave infrared system will replace the current 0.8-1.55μm band near-infrared system and become the development trend of the next generation of wireless laser communication technology.

There is very little research on 8-14μm wireless laser communication system technology using new devices in China, and no relevant research papers have been published yet. However, it is worth mentioning that in recent years, the development of 8-14μm long-wave infrared devices in China has been very rapid. The Shanghai Institute of Microsystem and Information Technology of the Chinese Academy of Sciences and other institutions are at the leading level in the field of long-wave infrared optoelectronic devices in China.

In summary, the new 8-14μm long-wave infrared wireless laser communication technology has demonstrated great technical advantages. Foreign research on this has lasted for many years, and the technology of key components has developed extremely rapidly. The conditions for system engineering have been basically met. Currently, various research institutions are actively working to make the system practical and commercial.