Optical Component Analysis and Application Field Analysis
2024-02-18 17:06:42
At present, security video surveillance still uses coaxial cables as the transmission medium for short-distance signal transceiving; with the impact of IP, TCP/IP protocol network transmission methods are also increasingly applied. However, no matter which transmission method, it can not meet the transmission needs of modern security. Optical terminal as a transmission medium terminal equipment, it becomes important in the entire transmission.
Optical transceiver classification and principle
The optical transmission system consists of three parts: a light source (optical transmitter), a transmission medium, and a detector (optical receiver). The work of the light source and the detector is performed by the optical transceiver. The Optical Multiplexer is a device that transforms multiple E1s (a data transmission standard for trunk lines, typically at 2.048 MbPS, which is adopted in China and Europe) into optical signals and transmits them. Its role is mainly to realize electro-optical and optical - Electric conversion). Optical transceivers mainly include analog optical transceivers and digital optical transceivers:
1, analog optical transceiver
The analog optical transceiver adopts the PFM modulation technology to transmit the image signal in real time, which is currently used more often. The transmitting end will first perform the PFM modulation of the analog video signal (generally, there are several methods of frequency modulation, phase modulation and amplitude modulation, so that the analog optical transceiver is divided into several optical transceivers such as frequency modulation, phase modulation and amplitude modulation), and then the electro-optical conversion is performed. After transmitting to the receiver, the optical-electrical conversion is performed, and then PFM demodulation is performed to recover the video signal. Due to the adoption of PFM modulation technology, the transmission distance can easily reach around 30Km, and the transmission distance of some products can reach 60Km, or even hundreds of kilometers. Moreover, the distortion of the image signal after transmission is very small, with high signal-to-noise ratio and little nonlinear distortion. By using wavelength division multiplexing technology, it is also possible to realize bidirectional transmission of image and data signals on one optical fiber.
2, digital optical transceiver
Since digital technology has obvious advantages in many respects compared with traditional analog technologies, just as digital technology has replaced analog technology in many fields, the digitalization of optical transceivers is also an inevitable trend. At present, digital image optical transceivers mainly have two technical methods: one is an MPEGII image compression digital optical transceiver, and the other is a non-compressed digital image optical transceiver.
The image compression digital optical transceiver generally adopts MPEGII image compression technology. It can compress moving images into N×2Mbps data streams and transmit them through a standard telecommunication interface or directly through optical fibers.
Due to the use of image compression technology, it can greatly reduce the signal transmission bandwidth to facilitate the use of less resources to transmit image signals. At the same time, thanks to the N×2Mbps standard interface, it is possible to use the rich channels of existing telecommunication transmission equipment to transmit surveillance images, which brings convenience to engineering applications. However, image compression digital optical transceivers also have their inherent disadvantages. Its fatal weakness is that it cannot guarantee the real-time performance of image transmission. Because image compression and decompression require a certain amount of time, a 1-2S delay is generally generated for the transmitted image. Therefore, this kind of equipment is only suitable for places with low requirement for real-time performance. In addition, the image will produce some distortion after compression, and the price of this optical transceiver is also high.
The principle of the uncompressed digital image optical transceiver is to carry out A/D conversion of the analog video signal and multiplex the signal of voice, audio, data, etc., and then transmit it through the optical fiber. It uses a higher data rate to guarantee the transmission quality and real-time performance of the video signal. Since the bandwidth of the optical fiber is very large, this high data rate does not put too much demands on the transmission channel. The uncompressed digital image optical transceiver provides excellent image transmission quality (signal-to-noise ratio is greater than 60dB, differential phase distortion is less than 2, differential gain distortion is less than 2%), achieves broadcast-grade transmission quality, and image transmission is fully real-time. Due to the adoption of digital technology, sophisticated communication technologies such as multiplexing and optical transceiver technologies can be used in the device to improve the reliability of the device and reduce costs.
Optical transceiver application field analysis
Video optical transceivers have entered the Chinese market for more than 20 years. The earliest applications of video optical transceivers were mainly focused on industries with relatively good funding, such as *,*, government, and video services, as well as industries requiring higher transmission efficiency. As domestic optical transceivers continue to mature and improve with technology, many fields are urgently applied to:
city ​​of peace
As we all know, the Safe City project is an extremely large and comprehensive management system. It involves a very wide range of issues. It not only needs to meet the requirements of urban public security management, traffic management, and emergency command, but also takes into account disaster accident warning, safety production monitoring, etc. On the other hand, the demand for image surveillance also needs to consider the system linkage needs of the government agencies, units, and companies that have established networks, and the integration of alarm, access control, and intercom systems, as well as linkage with broadcasting systems. In the Safe City project, the share of video optical transceivers is minimal, but the project is huge. In some large projects, the purchase amount of video optical transceivers can reach three to four million yuan.
highway
Over 200 kilometers of long-distance mechanical and electrical engineering tenders have appeared in highway projects in many provinces, and a large number of video optical transceivers are required in these projects. Therefore, as far as a single project is concerned, the purchase of optical transceivers has exceeded 2-3 million everywhere. Although the proportion of video optical transceivers in the highway construction cost of electromechanical engineering is still small, its role can not be ignored. The product quality and engineering quality of the video optical transceiver directly affect the operation of the entire monitoring system. Therefore, both Party A and system integrators attach great importance to the selection of video optical transceivers.
The highway sector has always been valued by mainstream video optical transceiver manufacturers. The competition among them has never been a shortage of “bloods.†However, due to the high requirements in technology, performance, production capacity, reliability, and after-sales service, it has determined the industry. Must be a heavy brand, heavy technology, high quality, heavy service, so there are not many brands that can enter the highway market, video and optical terminal market is still a real strength of the manufacturer's arena.
Urban Intelligent Transportation
After the late 1980s and early 1990s, with the acceleration of China’s industrialization process, a large number of populations have flooded into cities, and transportation problems have become increasingly prominent. In order to ensure the normal operation of urban transport, Beijing, Shenzhen, Shanghai, Nanjing and other cities have all established urban traffic monitoring networks. In the current IP network monitoring is not yet mature, most of the traffic information is transmitted through the optical fiber, video optical transceivers play a decisive role. In the monitoring of urban roads, video optical transceivers are mainly used for traffic statistics of city intersections, switching of traffic signals, capturing of illegal vehicles, and monitoring of traffic accidents. They are responsible for uploading these video information to traffic monitoring command centers to ensure The normal operation of city traffic.
Urban Rail Transit
With the rapid development of urban transportation and highway construction in our country, the requirements for equipment in the monitoring system are getting higher and higher. Because the optical fiber transmission has the advantages of wide bandwidth, long transmission distance and anti-interference, it is widely used. Due to its many transmission advantages and the drastic increase in market demand in recent years, optical transceivers have significantly reduced the cost of optical cables and have entered a relatively benign industrial development track.
At present, safe cities, urban intelligent transportation, highways, and urban rail transit projects are the major markets for optical transceivers. According to the forecast of authoritative agencies, the investment in China's urban rail transit market will reach 415.9 billion yuan in 2010-2015, with an average annual compound growth rate of 13.8%, of which, rail transit will be at least 2-3 billion yuan, and the annual domestic intelligent transportation system will be about The scale of investment of 20 billion yuan, video surveillance products account for about 16%, the annual new market demand is about 3.2 billion.
Optical transceiver classification and principle
The optical transmission system consists of three parts: a light source (optical transmitter), a transmission medium, and a detector (optical receiver). The work of the light source and the detector is performed by the optical transceiver. The Optical Multiplexer is a device that transforms multiple E1s (a data transmission standard for trunk lines, typically at 2.048 MbPS, which is adopted in China and Europe) into optical signals and transmits them. Its role is mainly to realize electro-optical and optical - Electric conversion). Optical transceivers mainly include analog optical transceivers and digital optical transceivers:
1, analog optical transceiver
The analog optical transceiver adopts the PFM modulation technology to transmit the image signal in real time, which is currently used more often. The transmitting end will first perform the PFM modulation of the analog video signal (generally, there are several methods of frequency modulation, phase modulation and amplitude modulation, so that the analog optical transceiver is divided into several optical transceivers such as frequency modulation, phase modulation and amplitude modulation), and then the electro-optical conversion is performed. After transmitting to the receiver, the optical-electrical conversion is performed, and then PFM demodulation is performed to recover the video signal. Due to the adoption of PFM modulation technology, the transmission distance can easily reach around 30Km, and the transmission distance of some products can reach 60Km, or even hundreds of kilometers. Moreover, the distortion of the image signal after transmission is very small, with high signal-to-noise ratio and little nonlinear distortion. By using wavelength division multiplexing technology, it is also possible to realize bidirectional transmission of image and data signals on one optical fiber.
2, digital optical transceiver
Since digital technology has obvious advantages in many respects compared with traditional analog technologies, just as digital technology has replaced analog technology in many fields, the digitalization of optical transceivers is also an inevitable trend. At present, digital image optical transceivers mainly have two technical methods: one is an MPEGII image compression digital optical transceiver, and the other is a non-compressed digital image optical transceiver.
The image compression digital optical transceiver generally adopts MPEGII image compression technology. It can compress moving images into N×2Mbps data streams and transmit them through a standard telecommunication interface or directly through optical fibers.
Due to the use of image compression technology, it can greatly reduce the signal transmission bandwidth to facilitate the use of less resources to transmit image signals. At the same time, thanks to the N×2Mbps standard interface, it is possible to use the rich channels of existing telecommunication transmission equipment to transmit surveillance images, which brings convenience to engineering applications. However, image compression digital optical transceivers also have their inherent disadvantages. Its fatal weakness is that it cannot guarantee the real-time performance of image transmission. Because image compression and decompression require a certain amount of time, a 1-2S delay is generally generated for the transmitted image. Therefore, this kind of equipment is only suitable for places with low requirement for real-time performance. In addition, the image will produce some distortion after compression, and the price of this optical transceiver is also high.
The principle of the uncompressed digital image optical transceiver is to carry out A/D conversion of the analog video signal and multiplex the signal of voice, audio, data, etc., and then transmit it through the optical fiber. It uses a higher data rate to guarantee the transmission quality and real-time performance of the video signal. Since the bandwidth of the optical fiber is very large, this high data rate does not put too much demands on the transmission channel. The uncompressed digital image optical transceiver provides excellent image transmission quality (signal-to-noise ratio is greater than 60dB, differential phase distortion is less than 2, differential gain distortion is less than 2%), achieves broadcast-grade transmission quality, and image transmission is fully real-time. Due to the adoption of digital technology, sophisticated communication technologies such as multiplexing and optical transceiver technologies can be used in the device to improve the reliability of the device and reduce costs.
Optical transceiver application field analysis
Video optical transceivers have entered the Chinese market for more than 20 years. The earliest applications of video optical transceivers were mainly focused on industries with relatively good funding, such as *,*, government, and video services, as well as industries requiring higher transmission efficiency. As domestic optical transceivers continue to mature and improve with technology, many fields are urgently applied to:
city ​​of peace
As we all know, the Safe City project is an extremely large and comprehensive management system. It involves a very wide range of issues. It not only needs to meet the requirements of urban public security management, traffic management, and emergency command, but also takes into account disaster accident warning, safety production monitoring, etc. On the other hand, the demand for image surveillance also needs to consider the system linkage needs of the government agencies, units, and companies that have established networks, and the integration of alarm, access control, and intercom systems, as well as linkage with broadcasting systems. In the Safe City project, the share of video optical transceivers is minimal, but the project is huge. In some large projects, the purchase amount of video optical transceivers can reach three to four million yuan.
highway
Over 200 kilometers of long-distance mechanical and electrical engineering tenders have appeared in highway projects in many provinces, and a large number of video optical transceivers are required in these projects. Therefore, as far as a single project is concerned, the purchase of optical transceivers has exceeded 2-3 million everywhere. Although the proportion of video optical transceivers in the highway construction cost of electromechanical engineering is still small, its role can not be ignored. The product quality and engineering quality of the video optical transceiver directly affect the operation of the entire monitoring system. Therefore, both Party A and system integrators attach great importance to the selection of video optical transceivers.
The highway sector has always been valued by mainstream video optical transceiver manufacturers. The competition among them has never been a shortage of “bloods.†However, due to the high requirements in technology, performance, production capacity, reliability, and after-sales service, it has determined the industry. Must be a heavy brand, heavy technology, high quality, heavy service, so there are not many brands that can enter the highway market, video and optical terminal market is still a real strength of the manufacturer's arena.
Urban Intelligent Transportation
After the late 1980s and early 1990s, with the acceleration of China’s industrialization process, a large number of populations have flooded into cities, and transportation problems have become increasingly prominent. In order to ensure the normal operation of urban transport, Beijing, Shenzhen, Shanghai, Nanjing and other cities have all established urban traffic monitoring networks. In the current IP network monitoring is not yet mature, most of the traffic information is transmitted through the optical fiber, video optical transceivers play a decisive role. In the monitoring of urban roads, video optical transceivers are mainly used for traffic statistics of city intersections, switching of traffic signals, capturing of illegal vehicles, and monitoring of traffic accidents. They are responsible for uploading these video information to traffic monitoring command centers to ensure The normal operation of city traffic.
Urban Rail Transit
With the rapid development of urban transportation and highway construction in our country, the requirements for equipment in the monitoring system are getting higher and higher. Because the optical fiber transmission has the advantages of wide bandwidth, long transmission distance and anti-interference, it is widely used. Due to its many transmission advantages and the drastic increase in market demand in recent years, optical transceivers have significantly reduced the cost of optical cables and have entered a relatively benign industrial development track.
At present, safe cities, urban intelligent transportation, highways, and urban rail transit projects are the major markets for optical transceivers. According to the forecast of authoritative agencies, the investment in China's urban rail transit market will reach 415.9 billion yuan in 2010-2015, with an average annual compound growth rate of 13.8%, of which, rail transit will be at least 2-3 billion yuan, and the annual domestic intelligent transportation system will be about The scale of investment of 20 billion yuan, video surveillance products account for about 16%, the annual new market demand is about 3.2 billion.
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