Research Progress on Passive Modulation in Free-Space Optical Communication

Traditional free-space optical communication requires both ends of the communication to be installed at the same time laser transmitting system, laser receiving system and acquisition, tracking and aiming system, resulting in the weight, volume, power consumption, equipment complexity, and technical difficulty of the system have been improved, thus limiting the development of free-space optical communication. Using the passive modulation technology constructed by asymmetric space laser communication link, the design of small volume, light weight, and low power consumption of the communication terminal is successfully realized, which provides convenience for the application of small- and medium-sized space laser communication technology. In this chapter, the research status of passive modulation at home and abroad is reviewed, which is mainly summarized abroad. In addition, the composition of the reverse modulation system and the working principle of the reverse modulator are described. Common Modulated Retro-Reflector such as Angle reflector reverse modulator and cat’s-eye reverse modulator are analyzed. The selection of wavelength and the size of optical receiver aperture are discussed. This chapter summarizes the different implementation types and characteristics of passive modulation, summarizes the application of passive modulation in optical wireless communication, and looks forward to the future development direction and prospect of this technology. In the future, passive modulation can be developed along the direction of high speed, focal plane pixelation, two-way communication, and coherent detection, and there is a lot of room for development. This chapter can provide a reference direction for the research of passive modulation and a new idea for the research of optical wireless communication.