Faced with the rapid development of the high-definition trend of the security industry, as an important part of video surveillance, the market development of high-definition optical transceivers will be bright. For optical transceiver manufacturers, it is imperative to adapt to the market demand and adjust the development strategy in a timely manner. Optical terminal classification principle The optical transmission system consists of three parts: a light source (optical transmitter), a transmission medium, and a detector (optical receiver). The operation of the light source and the detector is performed by the optical transceiver. The optical transceiver is a device that converts multiple E1 (a data transmission standard of a trunk line, usually at a rate of 2.048 MbPS, which is adopted in China and Europe) into an optical signal and transmits it (its function 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 uses PFM modulation technology to transmit image signals in real time, which is currently used more. The transmitting end first performs PFM modulation on the analog video signal (generally there are several methods of frequency modulation, phase modulation, and amplitude modulation, thereby dividing the analog optical transceiver into several optical transceivers such as frequency modulation, phase modulation, amplitude modulation, etc.), and then performing electro-optical conversion, optical signals. After being transmitted to the receiving end, optical-to-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 about 30Km, and the transmission distance of some products can reach 60Km or even hundreds of kilometers. Moreover, the image signal has a small distortion after transmission, and has a high signal-to-noise ratio and a small nonlinear distortion. By using wavelength division multiplexing, bidirectional transmission of image and data signals can also be achieved on a single fiber. 2, digital optical transceiver Because digital technology has obvious advantages in many aspects compared with traditional analog technology; just as digital technology has replaced analog technology in many fields, the digitization of optical transceivers is also an inevitable trend. At present, digital image optical transceivers mainly have two technical methods: one is MPEGII image compression digital optical transceiver, and the other is uncompressed digital image optical transceiver. Image compression digital optical transceivers generally use MPEGII image compression technology, which can compress moving images into N × 2 Mbps data streams through standard telecommunication communication interfaces or directly through optical fibers. Thanks to the image compression technology, it can greatly reduce the signal transmission bandwidth, so that it can transmit image signals with less resources. At the same time, due to the adoption of the N x 2 Mbps standard interface, it is possible to transmit surveillance images using the rich channels of the existing telecommunication transmission equipment, which brings convenience to engineering applications. However, image compression digital optical transceivers also have their inherent disadvantages. Its fatal weakness is that the real-time performance of image transmission cannot be guaranteed. Since image compression and decompression require a certain amount of time, a delay of 1-2S is generally generated for the transmitted image. Therefore, the device is only suitable for use in places where the real-time performance is not high. In addition, after compression, the image will have a certain distortion, and the price of the optical transceiver is also high. The principle of the uncompressed digital image optical transceiver is to perform analog A/D conversion on the analog video signal and multiplex the signals such as voice, audio, and data, and then transmit through the optical fiber. It uses a higher data rate to ensure 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 impose excessive requirements on the transmission channel. The uncompressed digital image optical transceiver provides good image transmission quality (signal-to-noise ratio greater than 60 dB, differential phase distortion less than 2, differential gain distortion less than 2), achieves broadcast-quality transmission quality, and image transmission is fully real-time. Due to the adoption of digital technology, the already mature communication technologies such as multiplexing technology and optical transceiver technology can be utilized in the device, thereby improving the reliability of the device and reducing the cost.
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The working principle and classification of optical transceiver
[ Huaqiang Security Network News ]