Free Space Optical Communication(FSO) is a communication technology that transmits information in a vacuum or the atmosphere using light waves as a carrier. FSO can be divided into atmospheric optical communications, inter-satellite optical communication and space-to-ground optical communication.
The space laser communication system refers to an optical communication system in which laser light waves are used as carriers and the atmosphere is used as a transmission medium. Free-space laser communication combines the advantages of optical fiber communication and microwave communication. It has the advantages of large communication capacity and high-speed transmission, and does not require the laying of optical fibers. Therefore, various technological powers have invested a lot of manpower and resources in the field of space laser communication, and have achieved great progress.
The atmospheric transmission laser communication system is a communication system composed of two laser communication devices that transmit modulated laser pulse signals (sound or data) to each other, receive and demodulate laser pulse signals from the other side, and realize duplex communication. The principle of a laser communication machine is that the system can transmit voice and perform data communication between computers. The modulated signal illuminates the laser through a power drive circuit such that the laser light carrying the speech signal is transmitted through the optical antenna. The other end of the laser communication machine gathers the collected optical signal to the photodetector through the optical antenna, then converts the optical signal into an electrical signal, and then amplifies the signal, detects the useful signal by the threshold detection method, and then solves the problem. The tuning circuit filters out the fundamental frequency component and the high-frequency component, restores the voice signal, and finally receives the voice communication through the power amplifier through the earphone. When the switch K is thrown down, data can be transferred for inter-computer communication, which is equivalent to a digital communication system. It consists of a computer, an interface circuit, a modem, an atmospheric transmission channel, and the like.
The interface circuit connects the computer and the modem so that the two can synchronize and coordinate work; the modulator converts or modulates the binary pulse into a waveform suitable for transmission on the channel, the purpose of which is to minimize the transmission result without changing the transmission result. The total power of the laser; demodulation is the inverse of the modulation, the inverse of the received modulated signal, the original digital signal is restored and sent to the interface circuit; the synchronization system is one of the important components of the digital communication system The role of the communication system is to have a unified time standard for the receiving and transmitting ends, and the pace is consistent.