Fiber optic communication is a communication method that uses light waves to transmit information and optical fibers as transmission media. It has the advantages of high speed and low loss, making it one of the main transmission methods. Digital optical transceiver is a signal transmission method with high transmission efficiency and good reliability. Its application is also very wide, and its technology is becoming more and more mature. Due to the intuitive, convenient, and widely applicable characteristics of video surveillance systems, video surveillance has been well developed in practical applications.
The digital video optical transceiver overcomes the drawbacks of analog video fiber optic transmission technology and can be applied in fields with poor conditions and high confidentiality requirements, with high practical value. The optical transceiver mainly consists of two parts: an optical transmitter and an optical receiver. The optical transmitter consists of three main parts: video signal processing, control signal processing, and optical transmission module. The optical receiver is mainly composed of video signal processing, control signal processing, and optical reception module. In the video signal processing section, it is mainly achieved through A/D or D/A conversion, line encoding and decoding, and parallel/serial (serial/parallel) conversion. The control signal processing circuit is composed of MAX489 and corresponding chips. The line encoding and decoding of the fiber channel adopts V HDL programming to implement 8B10B encoding and decoding. The optical transceiver module adopts a laser transceiver integrated module - NTR-22114T, which can achieve simultaneous transmission of video signals and control signals.
The optical transmission system consists of three parts: the light source (optical transmitter), the transmission medium, and the detector (optical receiver). The work of both the light source and the detector is completed by the optical transceiver. An optical transceiver is a device that converts multiple E1 (a data transmission standard for relay lines, typically at a rate of 2.048MbPS, adopted by China and Europe) signals into optical signals and transmits them (its main function is to achieve electrical optical and optical electrical conversion).
The digital transmission system converts the input signal into a pulse signal represented by "1" and "0", and uses it as the transmission signal. Restore it to its original information at the receiving end. In this way, the nonlinearity of the light source has little impact on the digital stream. In addition, digital communication can adopt some encoding and error correction methods, and is easy to implement multiplexing. Therefore, digital transmission systems have great advantages and have been widely used in many places.
There are mainly two types of optical transceivers: analog optical transceivers and digital optical transceivers. Due to the significant advantages of digital technology over traditional analog technology in many aspects; So just as digital technology has replaced analog technology in many fields, the digitization of optical transceivers is also an inevitable trend.
At present, there are two main technical methods for digital image optical transceivers: one is MPEGII image compression digital optical transceiver, and the other is non compression digital image optical transceiver.
Image compression digital optical transceivers generally use MPEGII image compression technology, which can compress moving images into N × 2Mbps data streams and transmit them through standard telecommunications communication interfaces or directly through optical fibers.
Due to the use of image compression technology, it can greatly reduce the signal transmission bandwidth, making it easier to transmit image signals with fewer resources. Meanwhile, due to the adoption of the N × 2Mbps standard interface, monitoring images can be transmitted using the abundant channels of existing telecommunications transmission equipment, which brings convenience to engineering applications. However, image compression digital optical transceivers also have their inherent drawbacks. Its fatal weakness is that it cannot guarantee the real-time transmission of images. Because image compression and decompression require a certain amount of time, there is usually a delay of 1-2 seconds for the transmitted image. Therefore, this device is only suitable for places that do not require high real-time performance. In addition, compressed images will produce certain distortions, and the price of this optical transceiver is also relatively high.