What is the role of an optical terminal in a surveillance system?

An optical terminal is a transmission device in an optical communication system, primarily performing optical-electrical conversion and transmission functions. It is generally used in telecommunications, power, surveillance, industrial control, video transmission, and other applications, with wide-ranging use across various industries. The commonly referred to optical terminal is the one used in surveillance systems to transmit integrated information such as video, data, Ethernet, and audio. It is mainly divided into analog optical terminals and digital optical terminals. Based on the different transmission media, there are single-mode optical terminals and multi-mode optical terminals.

Digital optical terminals digitize the image, voice, and data signals to be transmitted, then multiplex these digital signals to convert multiple low-speed digital signals into one high-speed signal, which is then converted into an optical signal. At the receiving end, the optical signal is restored to an electrical signal, the high-speed signal is decomposed back into the original multiple low-speed signals, and finally these data signals are restored to image, voice, and data signals. Analog optical terminals modulate the amplitude or frequency of the signal to be transmitted and then convert the modulated electrical signal into an optical signal. At the receiving end, the optical signal is restored to an electrical signal, and the signal is demodulated to recover the image, voice, or data signals.

Digital optical terminals offer high transmission signal quality and do not have the drawbacks of analog frequency-modulated, phase-modulated, or amplitude-modulated optical terminals, such as severe intermodulation interference during simultaneous transmission of multiple signals, susceptibility to environmental influences, poor transmission quality, and poor long-term operational stability. Therefore, digital optical terminals will gradually replace analog optical terminals.

Currently, in fields such as highways, transportation, electronic police, surveillance, security, industrial automation, power, customs, water conservancy, and banking, optical terminals for video images, audio, data, and Ethernet have begun to be widely and extensively applied. Figure 1 shows a typical application of an optical terminal.