The Role of Optical Terminals in Surveillance Systems

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

    A digital optical terminal digitally processes the image, voice, and data signals to be transmitted, then multiplexes these digital signals to convert multiple low-speed digital signals into one high-speed signal, and converts this signal into an optical signal. At the receiving end, the optical signal is restored to an electrical signal, the restored high-speed signal is decomposed into the original multiple low-speed signals, and finally these data signals are restored to image, voice, and data signals. An analog optical terminal modulates the amplitude or frequency of the signal to be transmitted and then converts 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 restore the image, voice, or data signals.

    Digital optical terminals offer high signal transmission 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, electric 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.