Optical transceiver is an optical fiber communication device that extends data transmission. It mainly uses signal modulation, photoelectric conversion and other technologies to utilize optical transmission characteristics to achieve long-distance transmission. Optical transceivers are generally used in pairs and are divided into optical transmitters and optical receivers. The optical transmitters perform electrical/optical conversion and transmit the optical signals out for optical fiber transmission; the optical receiver mainly restores optical signals received from optical fibers to Electrical signals complete the light/electrical conversion. The role of the optical transceiver is to transmit data remotely. However, it can be further subdivided into analog video optical transceivers and digital optical transceivers. What is the difference between them?
Signaling transmitted on the optical fiber is not the same on Optical <br> <br> analog optical signal emitted from the optical head is an analog optical modulation signal, the amplitude of the analog carrier signal with its input, frequency, phase change caused an optical signal amplitude, frequency, phase Changes are called amplitude modulation, frequency modulation, phase modulation optical transceivers. The optical signal transmitted by the optical head of the digital optical transceiver is a digital signal, that is, 0 or 1 corresponds to the strong or weak state of the optical signal. Different combinations of 0 and 1 represent video, audio, and data signals of different amplitudes.
Analog signal transmission input and output processing is not the same Regardless of analog and digital optical transceivers, the input baseband video, audio, and data signals must all be processed. For analog AM optical transceiver, the processing method is to modulate the amplitude of video, audio and data to a high-frequency carrier signal so that the amplitude of the high-frequency carrier signal varies with the amplitude of video, audio and data; and the digital optical transceiver is used for inputting. The baseband video, audio, and data are subjected to high-resolution analog-to-digital conversion. For example, a 1Vp-p amplitude range amplitude signal is represented by a 12-bit digital signal, and 1V is equally divided into 4096, so that the maximum voltage amplitude after analog-to-digital conversion is caused. The error is 1/4096V (about 2.5mV). This error voltage is called the quantization error voltage. The voltage values ​​of various amplitudes 0V, 1/4096V, 2/4096V, and 1V maximum correspond to the digital codes 000000000000000000000001 and 000000000010, respectively. ..111111111111. The digitally encoded signal directly controls the strong and weak states of the optical signal emitted by the optical head (corresponding to 0 or 1). The receiving optical unit then performs digital-to-analog conversion of the digital coding and restores the original baseband video, audio, and data signals.
Different ways of processing video <br> <br> caused, audio, data, signal distortion, distortion, due to interference of different simulation Optical be AM, FM, phase modulation, the amplitude of the analog signal varies due to the modulation of the carrier signal Whether the amplitude, frequency and phase changes caused by one-to-one linear relationship become the key to the quality of the optical transceiver. So far, it is difficult to achieve true linear modulation, non-linearity will inevitably cause signal distortion, and the modulated carrier is good. The signal also needs to modulate the optical signal. The nonlinearity of the optical signal is also a very important factor. As we all know, the non-linearity of the optical device has a great influence on the environmental temperature change, the stability of the operating voltage, and the optical emission power, so the optical device is During the production, 7-10 days of heat cycle aging and other process screening, aging, and testing can only be controlled to a certain extent in this conversion; optical signals in long-distance transmission in optical fiber will cause the power of the optical signal. Attenuation, transmission frequency drift, phase distortion, optical signal dispersion effects can also cause optical signal distortion; Signal arrives at the receiving end, the light receiving device still cause nonlinear distortion, the analog signal into the photoelectric conversion demodulated, demodulation and modulation as non-linear distortion is generated. Therefore, the synthetic analog optical transceiver, from the input signal modulation electro-optical conversion - optical output - photoelectric conversion - demodulation of the five processes, will cause non-linear distortion, and these signal distortion distortion is inherent, so it must be inevitably, so simulation Optical transmission of video images, audio quality, data is difficult to achieve very satisfactory results.
Crosstalk caused by simultaneous transmission of multiple signals In field monitoring applications, the user may have a variety of signals, such as video, audio, data, Ethernet, telephone, or other defined signals, one pair for each signal. The optical transceivers are expensive to transmit, so in order to increase the utilization efficiency of the optical fibers and reduce the cost, the necessary signals are multiplexed in the optical transceivers so as to be transmitted over a pair of optical fibers. For FM, AM and PM optical transceivers, it is difficult to transmit high-speed signals such as 10/100M Ethernet signals or multi-channel telephones. Multiple-channel video or audio signals are mixed in frequency modulation, amplitude modulation, and phase modulation on a single carrier. Inevitably will cause all kinds of mirroring, intermodulation interference. Therefore, there are many phenomena of mutual interference between FM, AM, and phase-shifting optical transceivers, audio, and data at the same time on the market. These unstable phenomena have always been inherent in analog modulation technology. Difficult to solve problems and shortcomings. Therefore, the analog optical transceiver has a limited capacity for transmitting signals and generally does not exceed the simultaneous transmission of four signals.
The stability of different analog-modulated optical transceivers adopts the carrier modulation method, and the carrier and the optical head are easily affected by the ambient temperature. There are disadvantages of the transmission quality changing with the environment. Because of this shortcoming, the maintenance of analog optical transceivers has become a headache for large-scale and important projects, which has also caused great dissatisfaction for many engineering contractors or owners. Therefore, choosing digital optical transceivers for some important projects is a wise choice.
Different prices Due to different architectures, the prices of analog optical transceivers and digital optical transceivers are slightly different. In general, single-channel video, audio, and data digital optical transceivers are slightly more expensive than single-channel analog optical transceivers, and more than four channels of video, audio, and data are digital. Optical transceivers are, on the other hand, much cheaper than analog optical transceivers, and the video quality after transmission is much higher than that of analog products. Therefore, the cost performance of digital optical transceivers is higher than that of analog video transceivers.
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