Analysis of the application field of video optical transceiver in video surveillance

Urban road traffic monitoring application

       Urban road traffic monitoring is one of the early applications of optical transceivers, and it is also a large consumer of optical transceivers. Its optical fiber network is characterized by numerous nodes and a star network structure. That is, each traffic crossing has an independent optical fiber connection to the command center. In terms of application requirements, in addition to the requirements for the return of video images at the monitoring point, it also involves high-speed dome control, networked control of semaphores, data return of electronic police, electronic guidance display control, and real-time flow detection data. Some places also require two-way audio functions. Therefore, when choosing an optical transceiver, in addition to video channels, 2 to 3 bidirectional RS232/485 data channels and 1 audio channel should also be provided. It should be noted that the data interface rate required by electronic police equipment is getting higher and higher, from 38.4K to 115.2K, and some even require a 10/100M Ethernet interface connection. In this way, higher technical requirements are put forward for the data port of the optical transceiver. In addition, because there are a large number of receivers that need to be placed in the command center, a high-density installation subrack that meets the standard 19-inch rack must be configured.

       High-grade highway monitoring should

       High-grade highway monitoring is currently concentrated on key sections such as toll stations, bridges and tunnels. Its obvious characteristics are large video capacity, long distance, chain network structure, and tight fiber resources. In terms of transmission interface requirements, in addition to large-capacity video ports, there are often two-way intercoms, such as interfaces that support AIPHONE intercom, telephone interfaces, and 10/100M Ethernet interfaces that meet automated office. In this case, generally use the digital optical transceiver coarse wavelength division multiplexing CWDM technology to network. At present, the larger video capacity of single-ended single-wavelength equipment of digital uncompressed optical transceiver is only 16 channels (2.5Gb rate). After adopting CWDM technology, 8 waves can meet the forward 128-channel video transmission, plus the reverse application of 1310nm wavelength It can form a complete large-capacity optical fiber transmission system. It should be pointed out that such a complex system needs to be confirmed by repeated demonstrations and calculations with the manufacturer. Uncertain issues should also require the manufacturer to simulate the engineering environment and build an experimental platform to demonstrate.

       Traditional technical defense monitoring application

       Technical defense monitoring is mainly aimed at parks, key parts, public places, financial and business places, etc. These application fields have different requirements for optical transceivers. They are mainly video in function, and supplemented by reverse control data interface to control lens pan/tilt Just use the alarm switch interface, and some have audio monitoring requirements. Because these application fields are extremely price sensitive, generally choose a lower-priced single-channel video analog optical transceiver or a cost-effective 4-channel video optical transceiver. Since general optical transceivers do not support the transmission of switching values, some manufacturers have specially designed switching value expansion interfaces to support this application. The audio interface of the optical transceiver is generally line level, that is, voltage type small signal. The input terminal must be connected to the pre-audio amplifier to connect the microphone, and the output terminal must be connected to the audio amplifier to drive the speakers. Therefore, when there is a monitoring requirement, pay attention to the front and rear configuration of the optical transceiver. It should also be noted that because general low-end analog optical transceiver products only configure one RS485 reverse data on the data channel, and generally only support a higher rate of 19.2Kb (or even lower), when they encounter some products, they can only use standard The matrix keyboard and high-speed dome controlled by RS485 half-duplex mode (also two-wire control, easy to confuse), and the 19.2Kb Manchester code that is Manchester code, will not work properly.

       Industrial TV monitoring application for large enterprises

       Due to the harsh electromagnetic environment and serious interference, large industrial and mining enterprises are the earliest industries to use optical transceivers for industrial TV monitoring. In this kind of application, it is mainly a large amount of video return, so choosing a pure video optical transceiver can meet the requirements. Many companies often require the monitoring equipment to be able to use the existing fiber resources because their internal data fiber network has been opened. At this time, some technical parameters and surplus fiber core conditions of the original fiber network must be understood. When the original fiber is a multimode fiber, it is also necessary to know whether it is a 50/125mm or 62.5/125mm multimode fiber. Otherwise, it will cause trouble when purchasing optical transceivers and matching pigtails.

       The high-end digital video optical transceivers require higher technical content, and they also have higher requirements for manufacturers in terms of design level, staff quality, process flow, and quality control. Especially the high-speed optical fiber transmission platform, high-speed digital multiplexing technology and precision manufacturing process are not available to ordinary manufacturers. For example, almost all manufacturers now claim to use the surface mount (SMT) production process. When the equipment is opened, it seems that they are using surface mount components, which seems to be the same. This is not the case. Due to the different scales of production between manufacturers, only manufacturers with large output and large-scale production will organize production in accordance with the standard SMT production process and adopt a fully automated surface mount production line with welding quality assurance. In terms of cost, a large number of small-scale manufacturers produce by hand-soldering SMD components. The damage to the chip by static electricity during the soldering process cannot be ignored. If there are only hidden dangers of missing soldering, false soldering and wrong soldering for the RC components with only two ends, but for the precision and large number of pins (up to 200 or more) of the QFP package used in some digital optical transceivers Said it may be the disaster of extinction. Because manual soldering causes the chip to receive different stresses in all directions, it is easy to damage the chip pins. The hidden dangers of such damage will not be immediate, but over time, they will gradually deform and cause the pins to break , So that the equipment fails after a period of work.