At present, as a whole of urban road traffic and community monitoring management, security monitoring has an increasingly large market cake, and various transmission applications emerge in endlessly. From the initial cable video coaxial transmission to the gradually popular optical cable transmission, the video transmission technologies adopted can be divided into coaxial baseband transmission, RF transmission, optical cable transmission, twisted pair transmission Digital network transmission, common cable transmission and other transmission modes. In addition to digital network transmission technology, others use physical transmission media. Each transmission mode has advantages and disadvantages. Below, we will discuss the advantages and disadvantages of several transmission modes.

1、 Video coaxial baseband transmission.

Monitoring engineering is the earliest, most used and relatively easy transmission mode in these transmission modes. Its transmission mode is direct transmission. One coaxial line is used to connect the camera to the monitoring center, and multiple lines are used for multiple channels. It is mainly through the outer shielding layer to resist interference and prevent the interference signal from entering the video transmission. The general transmission distance is 200-300m. If the distance is longer, anti-jamming device and video amplifier shall be added. One coaxial line transmits one channel of signal.

The characteristics of coaxial line are: small attenuation and good anti-interference; The disadvantage is that the wire diameter is thick, heavy and not easy to bend.

2、 RF transmission.
Firstly, multiple videos are transformed into one channel of RF signal input and transmission through a mixer, and then their own frequency band is selected through each channel of modem at the receiving end. Anti jamming crosses the jamming frequency band through frequency modulation. RF transmission has a "RF transmission network", which is complex. The key to the success or failure of RF transmission engineering. Including modulation, mixing, multi-channel averaging and many other technologies. Therefore, professional personnel are required for installation and commissioning. One coaxial line can transmit multiple signals. RF amplifier shall also be added for long-distance transmission.

Features: it is also a transmission line, which will not occupy a lot of space and has small attenuation; The disadvantage is that the modulation is complex.

3、 Optical cable transmission (optical fiber transmission).
Analog optical transceiver and digital optical transceiver are common in monitoring engineering. They are the best solution to solve the TV monitoring transmission of tens or even hundreds of kilometers. They are transmitted in optical fiber by converting video and control signals into laser signals. Long distance transmission, several kilometers to tens of kilometers. An optical fiber can transmit multiple signals. Minimum transmission attenuation. However, the remote laying and later maintenance of optical fiber are very difficult and costly. The transmitter receives the electrical signal, converts it into an optical signal through electro-optic conversion, and transmits it through optical fiber. The receiver then converts the optical signal into an electrical signal through photoelectric conversion, so as to realize the signal transmission. Through AM and FM, multiple signals can be transmitted in an optical core, and reverse data can also be transmitted.